
Glass. 



Book 



PRINCIPLES 



OP 



CHEMICAL PHILOSOPHY. 



BY 






JOSIAH P: COOKE, Jr., 

IRVING PROFESSOR OP CHEMISTRY AND MINERALOGY IN HARVARD COLLEGB. 



SECOND EDITION, 

REVISED AND CORRECTED. 



BOSTON: 
JOHN ALLYN, PUBLISHER, 

LATE SEVER, FRANCIS, & CO. 
1872. 



QT\ 



3| 

£-77 
\872 



Entered according to Act of Congress, in the year 1871, by 

JOSIAH P. COOKE, JR., 

in the Clerk's Office of the District Court of the District of Massachusetts. 



Mj tnuuu* 

JUL 2 1914 



University Press: Welch, Bigelow, & Co., 
Cambridge. 



PREFACE 

TO THE SECOND EDITION. 



The object of the author in this book is to present the phi- 
losophy of chemistry in such a form that it can be made with 
profit the subject of college recitations, and furnish the teacher 
with the means of testing the student's faithfulness and ability. 
With this view the subject has been developed in a logical 
order, and the principles of the science are taught indepen- 
dently of the experimental evidence on which they rest. It 
is assumed that the student has already been made familiar 
with this evidence, and with the more elementary facts which 
the philosophy of the science attempts to interpret. At most 
of our American colleges 4hss<instruetion is given in a course 
of experimental lectures ; but for less mature students a course 
of manipulation in the laboratory wilt be"> found a far more effi- 
cient mode of teaching, and some preliminary training of this 
kind ought to be made one of the requisites for admission to 
our higher institutions of learning. 1 The author has found by 
long experience that a recitation on mere facts, or descriptions 
of apparatus and experiments, is to the great mass of college 
undergraduates all but worthless, while the study of the phi- 
losophy of chemistry may be made highly profitable both for 
instruction and discipline. It must never be forgotten, how- 
ever, that chemistry is peculiarly an experimental science, and 
that the chief value of its culture in a college course depends 
on the facilities which it affords for cultivating the power of 
observation, and for teaching the methods of experimental in- 

1 For such a course of practical study the student can desire no better guide 
than the excellent work of Professors Eliot and Storer, recently published, 
"A Manual of Inorganic Chemistry, arranged to facilitate the Experimental 
Demonstration of the Facts and Principles of the Science." By C. \V. Eliot 
and F. H. Storer. New York, 1868. 



iv PREFACE. 

vestigation. It is not to be expected or desired that many of 
our college graduates should become professional chemists, but 
it is all important that every man of culture should understand 
or at least appreciate the methods and the inductive logic of 
physical science. The elementary facts of chemistry can be 
efficiently taught only by leading the student to observe for 
himself the phenomena in which they appear, and the attempt 
to learn them memoriter from a text-book will not only fail in 
its immediate object, but miss the chief end of scientific study. 
The author, therefore, would most earnestly deprecate the use 
of this book except as supplementary to some course of labora- 
tory or lecture-room instruction. It is only after the student 
has become, in some limited measure at least, familiar with 
chemical phenomena, that he is prepared to study the science 
in a systematic way ; but all who have this preparation will 
acquire most rapidly a general knowledge of the whole field 
when the subject is presented in a condensed and deductive 
form. The author has had especially in view this class of stu- 
dents, and has endeavored to meet their wants. 

Part I. of the book contains a statement of the general laws 
and theories of chemistry, an explanation of its nomenclature 
and mode of symbolical notation, together with so much of the 
principles of molecular physics as are constantly applied in 
chemical investigations. It might be figuratively called a 
grammar of the science. It is intended to be studied inde- 
pendently in consecutive lessons, and is adapted for class-room 
recitations, which should be accompanied, however, by such 
experiments or further explanations as the teacher may find 
necessary to render the subject intelligible. 

Part II. of the book presents the scheme of the chemical 
elements. It should only be studied in connection with exper- 
imental lectures or laboratory work, and will be found chiefly 
useful for systematizing and reviewing the facts and phenomena 
observed in the lecture-room or laboratory. It is in fact a note- 
book intended to aid the student in gaining the greatest benefit 
from a course of systematic lectures, enabling him to insure 
the accuracy of his knowledge, and giving the teacher the 
means of testing the student's acquirements. 

The value of problems as means of culture and tests of at- 
tainment can hardly be overestimated, and they have therefore 



PREFACE. V 

been made a chief feature in this book. Since those which 
are here given are chiefly intended as guides to the student, 
the answers have always been added ; and where the method 
was not obvious, the chief steps in the solution have been given 
as well. Every teacher will be able to multiply problems after 
these models to suit his own requirements. 

The questions, which accompany the problems, form another 
essential feature in the plan of instruction here presented. 
They are intended not only to direct the student's attention to 
the most important points, but also to stimulate thought by sug- 
gesting inferences to which the principles stated legitimately 
lead. 

These questions, moreover, will indicate to the teacher the 
manner, in which it is intended that the book should be studied. 
Care should be taken not to overstrain the memory, but to dis- 
tribute the necessary burthen through many lessons. Thus, for 
the first seven chapters, the student should not be expected to 
reproduce the symbols and reactions, nor even to call the 
names of the substances represented, except those of the sub- 
stances with which he is familiar. It will be sufficient for 
the time if he understands the principles which the symbols 
illustrate, and the relations of the parts of the reactions, al- 
though as yet these conventional signs may have for him no 
more definite meaning than the paradigms of a grammar. As 
he advances through chapters VIII. and IX., he should be 
expected to familiarize himself with the names of the com- 
pounds, and should begin to reproduce the symbols. When 
reciting on chapter X. he should be called upon to give not 
only the names of all the symbols, but also the symbols corre- 
sponding to all the names, and so on for the rest of the book. 
In reviewing the book a full knowledge of the names and sym- 
bols will be of course expected from the first. The questions 
and problems appended to each chapter will give the student 
a clear idea of what, in any case will be required. The author 
has been in the habit of writing out, for his own class, similar 
problems on separate cards, together with the names, symbols, 
reactions or other data, which may in any case be given. 
These cards are distributed at the beginning of each recitation, 
and the student is not called upon to recite until he has placed 
his work upon the blackboard. This plan obviates many prac- 
tical difficulties, and has been found to work with great success. 



vi PREFACE. 

In arranging the chapters of Part I. the only aim has been 
to present the several subjects in a logical sequence, and in 
other respects the order adapted is not always the most philo- 
sophical ; but the teacher can of course vary the order at 
pleasure. So also in regard to Part II., the teacher may pre- 
fer to take up the elements in his lectures in a different order 
from that in which they are there classified, but then the sev- 
eral sections may be studied in any order he would be likely to 
adopt with equal advantage. 

The philosophy of chemistry has been developed in this 
book according to the " modern theories " ; and the author 
would acknowledge his obligations to the recent works of 
Frankland, Kekule, Miller, Naquet, Roscoe, Watts, William- 
son, and Wurtz, all of which he has freely consulted. Care- 
ful attention has been given to the chemical notation ; and a 
method has been devised of writing rational symbols which, 
while it fully exhibits the relations of the parts of the mole- 
cule, condenses the formulas, and saves space and labor in 
printing. The nomenclature adopted accords with what the 
author regards as the best English usage. Innovations would 
hardly be justified in an elementary work, but every one must 
regret that the usage is not more uniform and consistent with 
the modern chemical philosophy. In the chapter on this sub- 
ject, the old names are given with the new. Lastly, the me- 
tric system of weights and measures, and the centigrade scale 
of the thermometer, are used throughout the book. 

In reviewing the work for a new edition, the chapter on the 
Electrical Relations of the Atoms has been rewritten, and the 
facts presented in the light of a new theory, which it is hoped 
will bring them into more intelligible relations. Important 
additions have also been made to the chapters on Stochiometry 
and Chemical Equivalency, and a new chapter has been added 
which treats of a number of interesting but highly complex 
compounds that were not included in the general plan of the 
book, and may be more advantageously studied in an appen- 
dix. Moreover, throughout the book the text has been altered 
wherever corrections have been made necessary by the recent 
progress of the science. 

Cambridge, September 1, 1871. 



CONTENTS. 



PART I. 

Chapter Page 

I. Introduction 1 

II. Fundamental Chemical Relations ... 7 

III. Molecules 11 

IV. Atoms . 24 

V. Chemical Notation ....... 33 

VI. Stochiometry 41 

VII. Chemical Equivalency 54 

VIII. Chemical Types 62 

IX. Bases, Acids, and Salts 80 

X. Chemical Nomenclature 100 

XL Solution and Diffusion 107 

XII. Thermal Relations of the Atoms . . .114 

XIII. Molecular Weight and Constitution . . .126 

XIV. Crystalline Forms 137 

XV. Electrical Relations of the Atoms . . . 155 

XVI. Relations of the Atoms to Light . . .174 

XVII. Chemical Classification 191 



Vin CONTENTS. 



PART II. 

Chapter Pagb 

XVIII. The Perissad Elements 201 

Division I. Hydrogen 201 

" II. Fluorine. — Chlorine. — Bromine. — Iodine 207 

a III. Sodium. — Potassium 213 

IV. Silver 220 

" V. Thallium .222 

VI. Gold 222 

" VII. Boron 228 

" VIII. Nitrogen. — Phosphorus. — Arsenic. — Anti- 
mony. — Bismuth 233 

" IX. Vanadium . . . . . . . 291 

" X. Uranium 293 

" XI. Columbium. — Tantalum 296 

XIX. The Artiad Elements 300 

Division I. Oxygen 300 

" II. Sulphur. — Selenium. — Tellurium . . 308 

" III. Molybdenum. — Tungsten . . . . 321 

" IV. Copper. — Mercury 328 

" V. Calcium. — Strontium. — Barium. — Lead . 340 
" VI., VII. Magnesium. — Zinc. — Indium. — Cadmium 354 
" VIII., IX. Glucinum. — Yttrium. — Erbium. — Ceri- 
um. — Lanthanum. — Didymium . . . 363 

" X. Nickel. - Cobalt 365 

" XL Manganese. — lion 373 

" XII. Chromium 398 

" XIII. Aluminum 408 

" XIV. to XVI. The Platinum Metals. — Ruthenium.— - 

Osmium. — Rhodium. — Iridium. — Palladium 418 

"XVII. to XIX. Titanium. — Tin. — Zirconium . . 430 

" XX. Silicon 444 

" XXI. Carbon. — Carbon and Oxygen, or Sulphur. — 
Carbon and Nitrogen. — Carbon and Hydro- 
gen. — Alcohols and their Derivatives . . 458 



XX. Appendix. Complex Amines and Amides, Chlorals, 

Mellitic Acid, Quinones, Electrical Measurements . 534 
Table I. French Measures. 
" II, Elementary Atoms. 
" III. Specific Gravity of Gases and Vapors. 

Logarithms and Antilogarithms 



FIRST PRINCIPLES 



OF 



CHEMICAL PHILOSOPHY. 



X/ 



PART I. 

CHAPTER I 

INTRODUCTION. 



1. Definitions. — The volumejot a body is the space it fills, i 
expressed in terms of an assumed unit of volume. The weighi 
of a bod}', as the word is used in chemistry and generally in 
common life, is the amount of material which the body con- 
tains compared with that in some other body assumed as the 
unit of weight. The specific gravity of a body is the ratio of Y 
its weight to that of an equal volume of some substance which 
has been selected as the standard. Solids and liquids are al- 
ways compared with water at its greatest density, which is at 

4° centigrade, and hence the numbers which stand for their 
specific gravities express how many times heavier they are 
than an equal volume of water at this temperature. Gases, 
however, are most conveniently compared with the lightest of 
all known forms of matter, namely, hydrogen, and in this book 
the number which indicates the specific gravity of a gas ex- 
presses how many times heavier it is than an equal volume of 
hydrogen, compared under the same conditions of temperature 
and pressure. 

2. Volume and Weight. — All experimental science rests 
upon accurate measurements of these fundamental elements, 
and it is therefore very important that there should be a gen- 
eral agreement among scientific men in regard to them. This 

1 



2 INTRODUCTION. 

has been secured by the almost universal adoption of the 
French system of measures and weights in all scientific inves- 
tigations. The details of this system are given in Table L, 
and they require no further explanation. Its great advan- 
tage over our ordinary English system is not only in its deci- 
mal subdivision, but also in the simple relation which exists 
between the units of measure and of weight. Since the unit 
of weight is the weight of the unit volume of water, and since 
the specific gravity of solids and liquids is always referred to 
water, as the standard, it is always true in this system that 

W= VX Sp. Gr. [1] 

If the volume is given in cubic centimetres, the weight ob- 
tained is in grammes ; but if the volume is given in cubic deci- 
metres or litres, the weight is found in kilogrammes. In this 
formula, Sp. Gr. stands for the specific gravity referred to 
water. If the specific gravity is referred to hydrogen, as in 
the case of gases, the value must be reduced to the water- 
standard before using it in the formula. The reduction is 
easily made, by multiplying by 0.0000896, a fraction which 
is simply the specific gravity of hydrogen itself referred to 
water. Using Sp. Gr. to represent the specific gravity of a 
gas referred to hydrogen, the formula becomes 

W=z VX Sp. Gr. X 0.0000896, [2] 

and may then be used in all calculations connected with the 
weight and volume of aeriform bodies. In such calculations, in 
order to avoid the long decimal fractions which the use of the 
gramme entails, Hofmann has proposed to introduce into 
chemistry a new unit of weight which he calls the crith. This 
unit is the weight of one cubic decimetre or litre of hydrogen 
gas at the standard temperature and pressure, and is equal to 
0.0896 grammes. If now we estimate the weight of all gases 
in criths, and let W represent this weight, while W represents 
the weight in grammes, and V the volume in litres, we shall 
also have 

W = V X Sp. Gr. and W= W X 0.0896, [3] 

and all problems of this kind will then be reduced to their 
simplest terms. 



INTRODUCTION. 3 

The specific gravity of gases is also frequently referred to 
dry air, which for many reasons is a convenient standard. 
The weight of one litre of air under standard conditions is 
1.293187 grammes. Hence, representing specific gravity re- 
ferred to air by Sp. (&x. we have 

Sp. Gr. : gp. <®x. = 1.2932 : 0.089G, 



or 
and 



Sp. Gr. = 0p.©r. X 14.42, 
0p. <5x. = Sp. Gr. X 0.06929. 



3. Chemistry and Physics. — Among material phenomena 
we may distinguish two classes. First, those wliich are mani- 
fested without a loss of identity in the substances involved. 
Secondly, those which are attended by a change of one or 
more of the materials employed into new substances. The 
science of chemistry deals with the last class of phenomena, 
that of physics with the first, and hence the terms chemical 
and physical phenomena. An illustration will make this dis- 
tinction plain. When a bar of iron is drawn out into wire, is 
rolled out into thin leaves, is reduced by mechanical means to 
powder, is forged into various shapes, is melted and cast into 
moulds, is magnetized, or is made the medium of an electric 
current, since the metal does not in any case lose its identity, 
the phenomena are all physical. When, on the other hand, 
the iron bar rusts in the air, is burnt at the blacksmith's forge, 
or is dissolved in dilute sulphuric acid, the iron is converted 
into a new substance, iron rust, iron cinders, or green vitriol, 
and the phenomena are chemical. The distinction between 
these two departments of human knowledge is not, however, 
so strongly marked as the definition would seem to imply. 
In fact they coalesce at many points, and a knowledge of the 
elements of physics is an essential preliminary to the successful 
study of chemistry. In the following pages it will be assumed 
that the student is acquainted with the most elementary princi- 
ples of this science, and references will be made to the sections 
of the author's work on Chemical Physics. The same rela- 
tion which physics bears to chemistry on the one side, chemis- 
try bears to physiology and the natural-history sciences on the 
other. 



4 INTBODUCTIQN. 

Questions and Problems. 

1. Reduce by Table I. at the end of the book, 

30 Inches to fractions of a metre. Ans. 0.7619 metre. 

76 Centimetres to inches. Ans. 29.92 inches. 

36 Kilometres to miles. Ans. 22.38 miles. 

10 Metres to feet and inches. Ans. 32 ft. 9.7 inches. 

1 Cubic metre to quarts. Ans. 880.66 quarts. 

1 Cubic foot to litres. Ans. 28.31 litres. 

1 Pint to cubic centimetres. Ans. 567.8 c. in. 8 

1 Litre to cubic inches. Ans. 61.027 cubic inches. 

1 Pound Avoirdupois to grammes. Ans. 453.6 grammes. 

1 Kilogramme to ounces avoirdupois. Ans. 35.27 ounces. 

1 Ounce to grammes. Ans. 28.35 grammes. 

2. If the globe were a perfect sphere what would be the circum- 
ference and what the diameter in kilometres ? 

Ans. Circumference 40,000 kilometres, 
Diameter 12,732.4 " 

3. The length of the metre was determined by measuring the dis- 
tance between Dunkirk (in France), Latitude 51° 2' 9" and For- 
mentera (one of the Balearic Islands), Latitude 38° 39' 56", both 
on the same meridian. This distance was found by triangulation to 
be equal to 730,430 toises. What is the length of a metre in terms 
of this old French unit of measure ? What, also, was the length 
measured in English miles ? No account is to be taken of the ellip- 
ticity of the earth. Ans. The metre, 0.5314 toise. 

The length was 854 miles. 

4. The Sp. Gr. of iron is 7.84. What is the weight of 10 c~m. 3 
of the metal in grammes ? What is also the weight in kilogrammes 
of a sphere of iron whose diameter equals one decimetre ? 

Ans. 78.4 grammes and 4.105 kilogrammes. 

5. What is the weight in grammes of 50 cTUT. 3 of oil of vitriol, 
when the Sp. Gr. of the liquid is 1.8? Ans. 90 grammes. 

6. The Sp. Gr. of alcohol being 0.8, what volume in litres would 
weigh 7.2 kilogrammes? Ans. 9 litres. 

7. Assuming that the earth is spherical, and its mean Sp. Gr. 5.67, 
what would be its weight, using as the unit of weight a kilometre 
cube of water at its greatest density ? Ans. 6,130,000,000,000. 

/ 8. Determine the Sp. Gr. of absolute alcohol from the following 
data: — weight of empty bottle 4.326; weight of same filled with 
water 19.654 ; weight of same filled with alcohol 16.741. 

Ans. 0.8095. 



INTRODUCTION. 5 

/ 9. Determine the Sp. Gr. of lead from the following data : — 
/weight of bottle filled with water 19.654; weight of lead shot 
15.456 ; weight of bottle filled in part with the shot and the rest 
with water 33.766. Ans. 11.5. 

10. Determine the Sp. Gr. of iron from: — weight of iron in air 
3.92 , weight under water 3.42. Ans. 7.84. 

1 1 . Determine Sp. Gr. of wood from : — weight of wood in air 
25.35 ; weight of sinker under water 9.77; weight of wood with 
sinker under water 5.10 grammes. Ans. 0.8445. 

12. How much volume must a hollow sphere of copper have, 
weighing one kilogramme, which will just float in water? What 
must be the volume of the copper ? Sp. Gr. of copper 8.8. 

Ans. One cubic dicemetre and 113.6 c. m. 3 

13. How much volume must a hollow cylinder of iron have, which 
weighs 10 kilogrammes and sinks one half in water, and what must 
be the volume of the metal ? Ans. 20 and 1.276 cubic decimetres. 

14. What is the weight in grammes (under standard conditions) 
•of 128 c.~m. 3 of oxygen gas (Sp. Gr. = 16) ? 

Ans. 0.1834 grammes. 

15. How many litres of carbonic anhydride gas (Sp. Gr. = 22) 
would weigh (under normal conditions) 4.480 kilogrammes? 

Ans. 2274 litres. 

16. Solve the last two problems by [3], and show in what respect 
the method differs from that indicated by [2]. 

17. What is the weight in criths (under standard conditions) of 
one litre of nitrogen gas (Sp. Gr. = 14), of one litre of chlorine gas 
(Sp. Gr. = 35.5), of one litre of marsh gas (Sp. Gr. = 8), and of 
one litre of ammonia gas (Sp. Gr. = 8.5) ? 

Ans. 14, 35.5, 8, and 8.5 criths respectively. 

18. What is the weight in grammes of one litre of each of the 
same gases under the same conditions ? 

Ans. 1.254, 3.180, 0.7165, and 0.7617 respectively. 

19. The weight of one litre of hydrochloric acid gas is 1.642 
grammes; of carbonic oxide gas 1.2500 grammes; of cyanogen gas 
2.335 grammes, and of hydrogen gas 0.0896 grammes. What is the 
specific gravity of each of these gases referred to air ? 

Ans. 1.270, 0.9665, 1.806, and 0.0693 respectively. 

20. What is the volume (under standard conditions) of 12.54 
grammes of nitrogen gas, when specific gravity referred to air is 
0.9703? Ans. 10 litres. 



6 INTRODUCTION. 

21. What is the weight of one litre of air in criths? 

Ans. 14.42. 

22. What would be the ascensional force of one thousand litres 
of hydrogen, under normal conditions ? 

Ans. The ascensional force is the difference between the weight 
of the hydrogen and that of the air displaced. Hence in 
the present example, the ascensional force would be 14,420 
— 1000 = 13420 criths, or 1,201 grammes. 

23. What is the value of a crith in grains, English weight. 

Ans. 1.382 grains. 






CHAPTER II. 

FUNDAMENTAL CHEMICAL RELATIONS. 

4. Compounds and Elements.- — With sixty-three exceptions, 
all known substances, by various chemical processes, may- 
be decomposed, and hence are called chemi cal compound s ; 
while the sixty-three substances which have as yet never 
been resolved into simpler parts are called chemical elements. 
There is some reason for believing that manv^if "not all, of 
these elementary substances may hereafter be decomposed, and 
hence they can only be considered chemical elements provis- 
ionally ; but, however this may be, all known materials may still 
be regarded as formed by the union of the particles of one or 
more of these sixty-three substances. A list of the chemical 
elements is given in Table II. The names of the more abun- 
dant or otherwise more important elements are printed in Ro- 
man letters. The others are very rare substances, and are 
practically unimportant. Of these elementary substances more 
than three fourths possess metallic properties, and among them 
are all the useful metals, including the liquid metal mercury. 
The rest present every variety of physical character. Oxygen, 
hydrogen, and nitrogen are permanent gases. Chlorine, and 
probably fluorine, though gases under ordinary conditions, may 
by pressure and cold be condensed to liquids. Bromine is a 
very volatile liquid; and among the solids we have every gra- 
dation between the highly volatile iodine, or the easily fusible 
phosphorus, on the one hand, and carbon, which has never 
even been melted, on the other. We find, also, among the ele- 
ments every difference as regards density. Hydrogen gas is 
the lightest, and the metal platinum the heaviest substance 
known. Several of the elementary substances occur in a free 
state in nature, for example, oxygen and nitrogen in the at- 
mosphere, carbon in the coal beds, sulphur in the neighborhood 
of active volcanoes, iron in meteoric stones, while arsenic, an- 



8 FUNDAMENTAL CHEMICAL RELATIONS. 

timony, bismuth, copper, gold, silver, mercury, and platinum, 
with a few other rare associates, are sometimes found in a 
more or less pure state in metallic veins. Gold and platinum 
are usually found in a free condition, though as a rule slightly 
alloyed with their associated metals ; but all the other elements 
are generally found in combination, and the greater number 
appear in nature only in this condition. From such compounds 
the elements may be extracted by various chemical processes, 
which will appear as we proceed. Among these elements the 
useful metals are the tools of civilization, carbon is our uni- 
versal fuel, while sulphur, phosphorus, arsenic, chlorine, bro- 
mine, and iodine have found important applications in the arts, 
and are therefore articles of commerce ; but the greater number 
of the elements are only to be seen in the chemist's laboratory, 
and are solely objects of chemical investigation. The elements 
are distributed in nature in very unequal proportions. At 
least one half of the solid crust of the globe, eight ninths of 
the water on its surface, and one fifth of the atmosphere which 
surrounds it, consist of the one element, oxygen. Moreover, 
the other elements are usually found in combination with 
oxygen, so that oxygen may be regarded as the cement by 
which these elementary parts of the world are held together. 
Next in abundance is silicon, which, after oxygen, is the chief 
constituent of the rocks, and makes up about one fourth of the 
earth's crust. Silicon is always found combined with oxygen, 
and more than one half of the oxygen of the globe is in com- 
bination with this element. Hence, the compound of the two, 
which we call silica or quartz, must make up more than one 
half of our solid globe, at least as far as its composition is 
known. After silicon in the order of abundance would follow 
the elements aluminum, calcium, magnesium, potassium, so- 
dium, iron, carbon, sulphur, hydrogen, chlorine, nitrogen, 
which, without attempting to discriminate between them, make 
up altogether Yerj nearly the other fourth of the earth's mass ; 
for the remaining fifty elements — including all the useful 
metals except iron — do not constitute altogether more than 
one one-hundredth. Of the sixty-three known elements, then, 
thirteen alone make up at least y 9 ^ of the whole known mass 
of the earth. 

5. Analysis and Synthesis. — The composition of a chemical 



FUNDAMENTAL CHEMICAL RELATIONS. 9 

compound may be made evident in two ways. First, by break- 
ing up the compound into its constituent parts ; secondly, by 
reuniting these parts and reproducing the original substance. 
The first of these methods of proof is called analysis, the sec- 
ond, synthesis. The study of the processes by which the com- 
position of a body may be discovered, and the relative amounts 
of its various constituents determined, forms an important 
branch of practical chemistry, which is known as Chemical 
Analysis, and this is subdivided into Qualitative and Quantita- 
tive Analysis, according to the object we have in view. Syn- 
thesis is chiefly used to prove the results of analysis. 

6. Law of Definite Proportions. — Numberless analyses 
have proved that any given chemical compound always contains 
the same elements combined in the same proportions. Thus, 
when we analyze water, sugar, and salt, we always obtain the 
result given below ; and this result is invariable, saving small 
errors of observation, from whatever source these materials 
may be drawn. The composition is given in per cents, as is 
usual in such cases. 

Water (Dumas). Salt. Sugar (Peligot). 

Hydrogen, 11.112 Sodium, 39.32 Carbon, 42.06 

Oxygen, 88.888 Chlorine, 60.G8 Hydrogen, 6.50 

Oxygen, 51.44 



100. 100. 100. 

Chemists have not yet succeeded in making sugar by com- 
bining its elements, but the synthesis both of water and salt is 
easily effected, and illustrates still more forcibly the same law. 
Thus we may mix together hydrogen and oxygen gas in any 
proportion, but when, by passing an electric spark through the 
mixture, we cause the elements to combine, then the gases 
unite in the exact proportion indicated above, and any excess 
of one or the other which may be present is left over. The 
law of definite proportions gives to chemistry a mathematical 
basis ; for, since the analyses of all compounds have been made 
and tabulated in away that will be soon explained, it is always 
possible, when the weight of a compound is given, to calculate 
the weights of its constituents, and, when the weight of one of 
its elements is known, to calculate the weights of all the other 
elements present. 



10 FUNDAMENTAL CHEMICAL RELATIONS. 

7. Mixture and Chemical Compound. — The law of definite 
proportions gives a simple criterion for distinguishing between 
a mixture and a true chemical compound. In the first the ele- 
ments may be mixed in any proportion, but in the true com- 
pound they are always combined in definite proportions. Thus 
we may mix together copper-filings and sulphur in any propor- 
tion, but as soon as we apply heat, and cause the elements to 
combine, then the copper combines with one half of its own 
weight of sulphur, and the excess of either element above 
these proportions is discarded. Again, in a mixture however 
homogeneous, we can generally, by mechanical means alone, 
distinguish the ingredients. Thus, in the mixture just referred 
to, a microscope would show the grains of sulphur and metallic 
copper, with all their characteristic appearances ; and by means 
of carbonic sulphide we can easily dissolve out all the sulphur 
from the mixture ; but after the chemical union has taken 
place, the characteristic properties of the elements are merged 
in those of the compound, and no such simple mechanical sep- 
aration is possible. But although these distinctions are gener- 
ally sufficient, nevertheless we find in some alloys, in solutions, 
and in a few other classes of compounds, less intimate condi- 
tions of chemical union where these criterions fail. 

8. Law of Multiple Proportions. — It is generally the case 
that the same elements unite in more than one proportion, form- 
ing two or more different compounds. Now we always find 
that the proportions of the elements in such compounds are 
simple multiples of each other. This law is best illustrated 
by the compounds of nitrogen and oxygen, which are five in 
number, and have the names indicated in the table below. In 
order to make evident the law, we give, not the percentage 
composition as above, but the amount of oxygen, which is in 
each case combined with one and three fourths parts of nitro- 
gen. 

COMPOUNDS OF NITROGEN WITH OXYGEN. 



Nitrous Oxide, 


Nitrogen. 
By weight. 

1.75 


Oxygen. 
By weight. 

1 


Nitrogen. 
By volume. 

2 


Oxygen. 
By volume. 

1 


Nitric Oxide, 


1.75 


2 


2 


2 


Nitrous Anhydride, 


1.75 


3 


2 


3 


Nitric Peroxide, 


1.75 


4 


2 


4 


Nitric Anhydride, 


1.75 


5 


2 


5 






* 



CHAPTER III. 

MOLECULES. 



9. Molecules. — In order to bring the facts of chemistry into 
relation with each other, and unite them in an harmonious sys- 
tem, the following theory, first proposed by the English chemist, 
Dalton, and known as the Atomic Theory, is generally accepted 
by chemists. This theory assumes, in the first place, that every 
body, whatever its substance may be, is formed by the aggre- 
gation of minute particles of the same kind, which cannot be 
further subdivided without destroying the identity of the sub- 
stance. Thus a lump of sugar is an aggregate of minute 
particles of sugar. If the sugar is burnt, these particles will 
be further subdivided ; but the sugar will be thus changed into 
new substances. In like manner, a drop of water is an aggre- 
gate of minute particles of water. By passing a current of 
electricity through the drop, these particles will be subdivided, 
but then we shall have no longer water, but the two elemen- 
tary gases, oxygen and hydrogen. The smallest particles of 
any substance lohich can exist by themselves, we call molecules. 

10. Physical Properties of Matter. — The physical qualities 
of a body depend solely on the relations of its molecules. The 
physicist has therefore no occasion to continue the subdivision 
beyond the molecule, which is his unit. 

Solid. — In a solid the molecules firmly cohere, and the 
force which binds them together has been called cohesion. On 
the form and size of the molecules, and also on the mode of 
aggregation, is supposed to depend the crystalline form of each 
substance, which is one of the most important and character- 
istic properties of matter, and one to which we shall have 
occasion hereafter to refer. On certain relations of the mole- 
cules, which we do not fully understand, depend undoubtedly 
elasticity, tenacity, ductility or malleability, hardness, transpar- 
ency, diathermancy, and the allied qualities of solid bodies. 



12 MOLECULES. 

Liquid. — In the liquid condition of matter the molecules 
have more freedom of motion than in the solid, but still the 
motion is circumscribed within the liquid mass. Moreover, a 
certain cohesion still exists between the molecules, and on this 
depends the form of the rain-drop. The various phenomena 
of capillary action also are effects of the cohesion of the liquid 
molecules modified by their adhesion to the surfaces of solids, 
and the solvent power of liquids is a still further effect of the 
same mutual action. Connected also with this freedom of 
molecular motion is the property of liquids of transmitting 
pressure in all directions, and the well-known principles of 
hydrostatics to which it leads; but this property belongs to 
the third condition of matter as well. 

Gas. — In the aeriform condition of matter, the motion of 
the molecules is. only circumscribed by the walls of the con- 
taining vessel, or by some force acting on the mass from with- 
out. The molecules of a gas are constantly beating against 
the walls which confine them, and were they not thus restrained 
w T ould fly off into space. The molecules of the atmosphere 
are restrained by the force of gravitation, and, as they fly up- 
wards like a ball thrown into the air, they are at last brought 
to rest, and fall back again to the earth. Hence gases always 
exert pressure against any surface with which they are in con- 
tact, and we measure the pressure, or, as we frequently call it, 
the tension of the gas, by the height to which it will raise a 
column of mercury. Chem. Phys. (158). The instrument 
used for this purpose is called a barometer. 

The height of the mercury column which represents the 
pressure or tension of a gas is always represented by H. 

In our latitude, at the surface of the sea, the atmosphere in 
its normal conditions will raise a column of mercury 76 cm. 
high. Hence U = 76, and to this standard we always refer in 
comparing together the volumes of different gases. 

11. Mariotte's Law. — The most characteristic feature of 
the aeriform condition is the great change of volume which 
gases undergo, under varying pressure, and the special law 
of compressibility which they obey. If we represent by H 
and //' two conditions of pressure to which the same body of 
gas is at different times exposed, then the law is expressed by 
the formula 

V: V' = H> : K [4] 



MOLECULES. 13 

Moreover, since the specific gravity of a given mass of gas 
must be the greater the less its volume, it is also true that 

Sp. Gr. : Sp. Gr'. = H: W, [5] 

and lastlv, since the weight of a given volume of gas is obvi- 
ously proportional to its specific gravity, we also have 

W: W' = H. H\ [G] 

in which W and W represent the weight of an equal volume 
of the same gas under the two pressures if and H'. 

12. Heat a Manifestation of Molecular Motion. — The 
effects of what we call heat are supposed to be merely mani- 
festations of the motion of the molecules of bodies. The 
greater the moving power of the molecule, the more forcibly it 
strikes against our nerves of feeling, and hence the more in- 
tense is the sensation of heat produced ; and to the condition 
of matter which produces this sensation we give the name of 
temperature. The greater the moving power of the molecules, 
the higher the temperature ; the less the moving power, the 
lower the temperature. Moreover, since by the very defini- 
tion all molecules at the same temperature are in the condition 
to produce the same sensation of heat, we must assume further, 
that, whatever their size or weight, they must all have, at the 
same temperature, the same moving power. The light mole- 
cule of hydrogen must move much faster than the heavy mole- 
cule of carbonic anhydride in order to produce the same effect. 
If now Ave represent the mass of any molecule by m, and by V 
its velocity at any given temperature, then the moving power 
will be represented by ±m V% Chem. Phys. (42), and this will 
have the same value for every molecule at the same tempera- 
ture. With a few exceptions, all bodies expand with an in- 
creasing temperature, and in the case of mercury the change 
of volume is so nearly proportional to the change of tempera- 
ture that we may use the varying volume of a confined mass 
of this liquid as a measure of temperature. This is the sim- 
ple theory of the common mercurial thermometer, and in this 
book we shall refer all temperatures to the degrees of the cen- 
tigrade scale. These degrees are purely arbitrary ; but to 
each one corresponds a definite value of £m V' 2 , although we 
have not as yet been able to connect our arbitrary with our 
theoretical measure. 



14 MOLECULES. 

When we increase the temperature of a body, we must of 
course increase the moving power of all the molecules, each by 
the same amount, and the sum of the moving powers which 
they thus acquire is the legitimate measure of the amount of 
heat which the body receives. Hence, while ^m V' 2 represents 
the temperature of a body, 2 %m V 2 represents the whole 
amount of heat which it contains. Practically, however, we 
measure quantity of heat by an arbitrary standard, and we 
shall use in this book as our unit the amount of heat required 
to raise the temperature of a kilogramme of pure water from 
0° to 1° centigrade. This we call the Unit of Beat, and it 
has been found, by careful experiments, that this unit of heat 
represents an amount of moving power which is adequate to 
raise a weight of 423 kilogrammes one metre, or to do any 
other equivalent amount of work. 

13. Expansion by Heat. — The amount of expansion which 
bodies undergo when heated has been carefully measured for 
many different substances, and the results are tabulated in all 
works on physics. Chem. Phys. Table XV. In each case is 
given the coefficient of expansion, which is the small fraction 
of its volume which a body increases when heated one centi- 
grade degree. If, now, K represents this fraction, V the initial 
volume, V the new volume, t the initial temperature, and t' 
the new temperature, then, if we assume that the expansion is 
proportional to the temperature, we easily deduce the formula, 
Chem. Phys. (239), 

V>=V{l + K(t>-t)). [7] 

This formula serves to calculate the change of volume both 
of solids and gases, which expand, nearly at least, proportion- 
ally to the temperature. The same, however, is not true of 
liquids, whose rate of expansion frequently increases, with the 
temperature, very rapidly ; and for such bodies we are obliged 
to use the following formula, which is of the general form in 
which every algebraic function may be developed, and is much 
less simple : — 

V = V(l + At + Bt 2 + OT + Sfc). [8] 

In this formula, V represents the required volume at some 
temperature, t, and V, the volume at 0°, which is assumed to 
be known ; while A, B, C, &c, are numerical constants, which 



MOLECULES. 15 

have been determined by experiment in the case of most liquids. 
Chem. Phys. (255). 

Both solids and liquids expand with irresistible force, and 
we have, therefore, only this one effect to consider in regard to 
the action of heat upon them. It is different, however, with 
gases. By enclosing a gas in a tight vessel, we can raise its 
temperature without changing its volume, except so far as the 
vessel itself becomes enlarged by the heat. The effect of the 
heat is, then, to increase the tension or pressure of the gas. 
Hence, in the case of a gas, we may have two distinct effects ; 
first, an increase of volume, when the pressure is constant; 
secondly, an increase of tension, when the volume is constant. 
The increased volume may always be calculated from the in- 
itial volume and difference of temperature, by means of the 
formula, 

V'= V (1 + 0.00366 {t> — ()), [9] 

which differs from that just given only in that the numerical 
value has been substituted for K, — this being the same for all 
gases. On the other hand, the increased tension may always 
be calculated from the initial tension, by means of the corre- 
sponding formula, 

H> = H(\ + 0.00366 {t' — t)), [10] 

in which II and H' stand for the heights of the mercury col- 
umns which measure the initial and final tension respectively. 
The last formula is easily deduced from the first, on the prin- 
ciples of Mariotte's law, stated above. Chem. Phys. (261) 
and [201]. 

Variations of temperature produce such important changes 
in the volume and specific gravity of all bodies, and especially 
of gases, that it becomes frequently essential, before compar- 
ing together different observations, to reduce them all to some 
standard temperature. Most scientific men use, as this stand- 
ard temperature, 0° centigrade, and scientific measures are 
generally adjusted to this standard ; but 60° Fahrenheit, corre- 
sponding to 15°.5 centigrade, is often a more convenient stand- 
ard, because it is nearer the mean temperature of the air, and 
is, therefore, not unfrequently employed. 

14. Change of State. — Many substances are capable of ex- 



16 MOLECULES. 

isting in all the three conditions of matter. Now, we find that 
whenever a solid changes to a liquid, or a liquid to a gas, heat 
is absorbed ; and conversely, whenever a gas is liquefied, or a 
liquid becomes a solid, heat is evolved ; although, as a general 
rule, this change of state is accompanied by no change of tem- 
. perature. Thus, one kilogramme of ice, in melting, absorbs 
79 units of heat, although the temperature remains at 0° dur- 
ing the change ; and when, by boiling, a kilogramme of water 
is converted into steam, under the normal pressure of the air, 
no less than 537 units of heat disappear, although the tem- 
perature both of the steam and of the water is constant at 100° 
during the whole period. On the other hand, when the steam 
is condensed or the water frozen, absolutely the same amount 
of heat is set free as was before absorbed. The heat thus ab- 
sorbed or set free is generally called the latent heat of the liquid 
or gas, and in the case of many substances the amount has 
been carefully measured. Chem. Phys. (277) and (299). Ac- 
cording to the theory we are studying, these effects are the 
direct results of the molecular condition of matter. The change 
of state must be accompanied by a change in the relative position 
of the molecules, or in their distance from each other ; and this 
change, in its turn, must be attended with a destruction or pro- 
duction of the moving power on which the effects of heat de- 
pend. Chem. Phys. (215 bis.). 

15. Sources of Heat. — The sun is the original source of 
almost all the heat we enjoy on the earth, for the effect of the 
earth's internal heat, at its surface, is at best very small, — 
and all our artificial sources of heat have drawn their supply 
either directly or indirectly from the great central luminary. 
According to our theory the effect of the sun's rays is a simple 
result of the transfer of molecular motion from the sun to 
the earth, either by some unknown influence exerted from a 
distance, or else by an actual transfer of motion through the 
material particles of the ether, which is assumed to fill the in- 
tervening space. The great source of all artificial heat is com- 
bustion in its many forms, and this, as we shall hereafter see, is 
merely a clashing together of material molecules, and is neces- 
sarily attended with a great development of that moving power 
to which we refer all thermal effects. 

1 6. Specific Heat. — The amount of heat required to raise 



MOLECULES. 17 

to the same extent the temperature of equal weights of differ- 
ent substances is by no means the same. The quantity is capa- 
ble in any case of exact measurement, and is called the specific 
heat of the substance. The amount of heat required to raise the 
temperature of one kilogramme of water one centigrade degree 
has been assumed as the unit, and we express the specific heat 
of other substances in terms of this measure. Moreover, since 
with the exception of hydrogen the. specific heat of water 
is greater than that of any substance known, the specific heat 
of all other bodies must be expressed by fractional numbers. 
In every case, unless otherwise stated, the numbers indicate 
what fraction of a unit of heat would be required to raise the 
temperature of one kilogramme of the substance from 0° to 1° 
centigrade. Chem. Phys. (232). 

17. Molecular Condition of Gases. — The aeriform state 
is by far the simplest condition of matter, and there are two 
peculiarities in its properties which lead to important conclu- 
sions in regard to its molecular conditions. These character- 
istics are as follows : First, All true ga>es obey the same law 
of compressibility. SecondlyTTScpiiu 1 volumes of all true gases 
expand equally on the same increase of temperature. Chem. 
Phys. (2G2). Now, according to the mechanical theory of 
heat (§ 10) these peculiar relations of the aeriform condition 
of matter are best explained on 
volumes of all gases contain tiie 
and since, moreover, this theorel 
with almost all the facts of chemistry, it has been universally 
adopted as a fundamental -principle of the science. This 
peculiar molecular condition, however, is only found in the gas, 
for it is only in this state that the molecules are sufficiently 
separated from each other to be freed from the mutual action 
of those molecular forces which give rise to far more com- 
plicated relations in both liquid and solid bodies. Moreover, 
with our ordinary gases (in the degree of condensation in 
which they exist under the pressure of the atmosphere), the 
molecules are not yet sufficiently far apart to be wholly freed 
from the effects of their mutual action, and hence the theo- 
retical condition is not absolutely fulfilled ; and in vapors, 
where the molecules are still closer together, the variation 
from the theory is quite large. In proportion as the gas ex- 
2 



V- 



us of the aeriform condition 
the assumption that Equal v .\l 
same number of molecules; 

iticai deduction harmonizes 



/ 



18 MOLECULES. 

pands, the theoretical condition is approached, and, when in a 
state of great expansion, equal volumes of all gases would 
undoubtedly contain exactly the same number of molecules. It 
is only then that we reach the condition of what we have called 
above the true gas, and this is our criterion of its state, — that 
it obeys absolutely the law of Mariotte. A very important 
corollary follows at once from the principle we have just de- 
duced. 

The molecular weight of all substances is directly propor- 
tioned to their specific gravities in the state of gas. 

We have adopted in this book hydrogen gas as our unit of 
specific gravity for aeriform substances, and were we also to take 
the molecule of hydrogen as our unit of molecular weight, then 
the number which expresses the specific gravity of a gas would 
express also its molecular weight. But for reasons which will 
appear hereafter, we have selected the half hydrogen molecule 
as our unit, and hence the molecular weight, of any substance 
in terms of this unit is atwaylTwice its specific gravity in the 
state of gas. In Table III. we have given, according to the 
most accurate experimental data, the Sp. Gr. (referred to 
hydrogen) of all the best known gases and vapors, and in a 
parallel column we have also given the Half-molecular Weights 
of the same substances determined by chemical analysis, in a 
manner which will be hereafter described. It will be seen 
that the numbers in the second column are almost precisely 
the same as those in the first, and the slight differences 
which will be noticed, either arise from the fact that the 
vapors, under the conditions in which alone their Sp. Gr. 
can be accurately determined, are not true gases, that is, do 
not exactly obey Mariotte's law ; or in other cases, where 
the differences are more considerable, may be referred to a 
partial decomposition of the substance itself in the process of 
the experiment. In solving the problems of this book, and 
generally in most chemical problems, the Half-molecular weight 
may be taken as the true Sp. Gr. The logarithms of these 
values given in the last column of the table will be found useful 
in this connection. Although only given to four places of 
decimals, they exceed in accuracy the experimental data. The 
values in the column of £jp. (3t. referred to air, are given, as 
a rule, to one decimal place beyond the limit of error. 



MOLECULES. 19 

Questions and Problems. 

1. Are the qualities of a molecule of any substance, the same as 
those which distinguish the substance itself? 

2. What is the distinction between cohesion and adhesion ? 

3. When the barometer stands at 76 c. m., with what weight in 
grammes is the air pressing against each square centimetre of sur- 
face V Sp. Gr. of mercury 13.596. Ans. 1033. 

4. To what difference of pressure does a difference of one centi- 
metre in the barometric column correspond ? 

Ans. 13.596 grammes. 

5. When a mercury barometer stands at 76 c. m. how high would 
a water barometer stand ? Also, how high would barometers stand 
filled with alcohol or sulphuric acid, disregarding in each case the 
tension of the vapor? Sp. Gr. of alcohol 0.81 ; Sp. Gr. of sulphuric 
acid 1.85. Ans. 1033 ; 1275 and 558.2 c. m. 

6. A volume of hydrogen gas was found to be 200 c. m. 3 The 
height of the barometer observed at the same time, was 74 c. m. 
What would have been the volume if observed when the barometer 
stood at 76 c. m. Ans. 194.7 cTm. 3 

7. A volume of nitrogen standing in a bell-glass over a mercury 
pneumatic trough measured 250 cTnr. 8 The barometer at the time 
stood at 75.4 c. m., and the level of the mercury in the bell wa? 
found by measurement to be 6.5 above the surface of the mercury 
in the trough. Required to reduce the volume to standard pressure. 

Ans. The pressure of the air on the surface of the mercury in the 
trough (measured at 75.4 c. m.) was balanced first by the 
column of mercury in the bell, and secondly by the tension 
of the confined gas. Hence the pressure to which the gas 
was exposed was equal to 75.4 — 6.5 = 68.9 c. m. and we 
have 76 : 68.9 = 250 : x = 226.7 cTm: 8 

8. What would be the answer to the same problem, had the 
trough been filled with water ? 

Ans. The water column in the bell exerts a pressure which is as 
much less than the pressure of the mercury column in the 
previous problem, as the Sp. Gr. of water is less than the 
Sp. Gr. of mercury. Hence we have 13.6 : 1 = G.5 : 0.48, 
also 75.4 — 0.48 = 74.92, and 76 : 74.92 = 250 : x = 246.4 
c. m. 3 

9. A closed vessel, which displaces one litre of air, is poised on a 
balance with weights, whose volume is inconsiderable when com- 
pared with that of the vessel. The balance is in equilibrium when 



20 MOLECULES, 

the barometer stands at 76 c. m. If the barometer falls to 71 c. m. 
how much weight must be added to restore the equilibrium ? 

Ans. 85 milligrammes. 

10. Given the weight of one litre of dry air under the normal 
conditions as 14.42 criths, what will be the weight of one litre of 
dry air at the normal temperature, but under a pressure of 72 c m. ? 

Ans. 13.G7 criths. 

11. A volume of gas measures 500 c. tn. at 15° what will be its 
volume at 288°. 2 ? In this and the next three problems the pressure 
is assumed to be constant. Ans. 1000 c. m. 3 

12. To what temperature must an open vessel be heated before 
one quarter of the air which it contains at 0° is driven out ? 

Ans. 91°.07. 

13. An open vessel is heated to 819°.6. What portion of the air 
which the vessel contained at 0° remains in it at this temperature ? 

Ans. 1. 

14. A closed glass vessel, which at 13° was filled with air having 
a tension of 76 c. m. is heated to 559°.4. Determine the tension of 
the heated air. Ans. 3 atmospheres. 

15. Reduce the following volumes of gas measured at the tem- 
peratures and pressure annexed to 0° and 76 cm. 

1. 140 cTm. 3 H=57c. m. t — 136°.6 Ans. 70 c7m. 3 

2. 320 cTm~. 3 H = 95 c. m. t = 91°.l Ans. 300 cTnl. 3 

3. 480 cThT. 3 #=38 cm. t = 68 3 .3 Ans. 192 cm". 3 

16. What is the weight of dry air contained in a glass globe of 
640 c m. 3 capacity at the temperature 54G°.4 and under a pressure 
of 71.25 c m. Ans. 0.2583 grammes. 

General Solution. — In order to make the solution general we 
will represent the capacity of the globe, the temperature and the 
height of the barometer by V, t and H respectively. We can also 
easily find from Table III. that one cubic centimetre of dry air at 
0°, and when the barometer stands at 76 c m., weighs 14.42 criths 
or 0.001292 grammes. To find what one cubic centimetre would 
weigh when the barometer stands at H centimetres, we make use 
of proportion [6], whence we derive 

w = 0.001292 . 5, 

the weight of one cubic centimetre at 0° and under a pressure of 
H centimetres. To find what one cubic centimetre would weigh 



MOLECULES. 21 

under the same pressure but at t°, it must be remembered that one 
cubic centimetre at 0° becomes (1 -f- t 0.00366) cubic centimetres 
at t° [7] ; therefore at 1° and at H centimetres of the barometer 

o H 

(1 -f- 1 0.00366) cTui: weigh 0.00129 . — grammes. By equating 

these two terms we obtain 

(1 + *0.0036C) = 0.00129 . ~, 

whence 

1 H 



1 = 0.00129 



1 + * 0.00366 ' 76' 

the weight of one cubic centimetre at t° and under a pressure of 
H centimetres. The weight of V cubic centimetres (w) is evidently 

« = 0-00129 V. , + (0 1 0M6t .g 6 . DO a] 

Thus far in this solution we have neglected the change in capacity 
of the glass globe due to the change of temperature. This causes 
no sensible error when the change of temperature is small, but 
when the change of temperature is quite large the change of ca- 
pacity of the globe must be considered. If the capacity is V c. in. 3 
at 0° it becomes at t° V (1 -f t 0.00003). (See Chem. Phys. 
§§ 241 - 244.) Introducing this value for V into the above equa- 
tions we obtain 

«= 0.00129 V (1 + I 0.00003) . 1 + ,* 00366 . g. [10 J] 

17. Required a general method for determining the £m. (&X. °f 
a vapor. 

Solution. — The specific gravity of a vapor has been defined as its 
weight compared with the weight of the same volume of hydrogen 
gas under the same conditions of temperature and pressure, but 
practically it is most convenient to determine the Sn. Q5l\ with 
reference to air, and subsequently to reduce the result to the 
hydrogen standard. 

To find, then, the £m. (&t. °f a vapor, we must ascertain the 
weight of a known volume, V, at a known temperature, t, and under 
a known pressure, H, and divide this by the weight of the same 
volume of air at the same temperature, and under the same pressure. 
The method may best be explained by an example. Suppose, 
then, that we wish to ascertain the £m, Q?t. °f alcohol vapor. 
We take a light glass globe having a capacity of from 400 to 500 
c- in. 3 , and draw the neck out in the flame of a blast lamp, so as to 
leave only a fine opening, as shown in the figure at a. The first 



22 



MOLECULES. 




step is now to ascertain the weight of the glass globe when com- 
pletely exhausted of air. As this cannot readily be done directly, 

we weigh the globe full of air, and 
then subtract the weight of the air, 
ascertained by calculation from the 
capacity of the globe, and from the 
temperature and pressure of the 
air, by means of equation (10 a). 
Call the weight of the globe and air 
W, and the weight of the air w, then 
W — to is the weight of the globe 
exhausted of air. The second step 
is to ascertain the weight of the 
globe filled with alcohol vapor at 
a known temperature, and under a 
known pressure. For this purpose 
we introduce into the globe a few 
grammes of pure alcohol, and mount it on the support represented 
in the accompanying figure. By loosening the screw, ?% we next 
sink the balloon beneath the oil contained in the iron vessel, V, and 
secure it in this position. We now slowly raise the temperature of 
the oil to between 300° and 400°, which we observe by means of the 
thermometer, T. The alcohol changes to vapor, and drives out the 
air, which, with the excess of vapor, escapes at a. When the bath 
has attained the requisite temperature, we close the opening a, by 
suddenly melting the end of the tube at a with a mouth blowpipe, 
and as nearly as possible at the same moment observe the tempera- 
ture of the bath and the height of the barometer. We have now 
the globe filled with alcohol vapor at a known temperature, and 
under a known pressure. Since it is hermetically sealed, its weight 
cannot change, and we can therefore allow it to cool, clean it, and 
weigh it at our leisure. This will give us the weight of the globe 
filled with alcohol vapor at a known temperature, t\ and under a 
known pressure, II'. Call this weight W. The weight of the 
vapor is W' — W -f- w. The third step is to ascertain the weight 
of the same volume of air at the same temperature and under the 
same pressure. This can easily be found by calculation from equa- 
tion (10 h). The last step is to find the capacity of the globe, which, 
although we have supposed it known, is not actually ascertained 
experimentally until the end of the process. For this purpose we 
break off the tip of the tube («), under mercury, which, if the ex- 
periment has been carefully conducted, rushes in and fills the globe 
completely. We then empty this mercury into a carefully gradu- 
ated glass cylinder, and read off the volume. We find then the 



MOLECULES. 



23 



Sp. (?$£. by dividing the weight of the vapor by the weight of the 
air. The formulas for the calculation are then 



Weight of the globe and air, 



to = 0.001292 V. 



w. 

1 H 

1 + t 0.00366 ' 76' 

W — w. 



globe exhausted of air, 

" filled with vapor at a temperature t' and 

under a pressure H', W'. 

vapor, W — W -j- w. 

air at t' and under a pressure H', == 

0.001292 V (1 -|- t 0.00003) . - 



U.U0366 



Bp.©r. = 



W — W -f- w 



0.001292 V (1 + t' 0.00003) 



1. Ascertain the £jr). (St. ^ alcohol vapor from the following 
data : — 



"Weight of glass globe, W 

Height of barometer, II 

Temperature, t 
Weight of globe and vapor, W' 

Height of barometer, H' 

Temperature, t' 

Volume, V 



50.801 grammes. 

74.75 centimetres. 
18° 

50.824 grammes. 

74.76 centimetres. 
167° 

351.5 cubic centimetres. 
Ans. 1.575. 



2. Ascertain the £j« (g>r. of camphor vapor from the following 
data : — 



Weight of glass globe, 

Height of barometer, 

Temperature, 

Weight of globe and vapor, 

Height of barometer, 

Temperature, 

Volume, 



w 


50.134 


grammes. 


H 


74.2 


centimetres. 


t 


13°.5 




W 


50.842 


grammes. 


H' 


74.2 


centimetres. 


i' 


244° 




V 


295 


cubic centimetres. 
Ans. 5.371. 



CHAPTER IV. 

ATOMS. 

18. Definition — The atomic theory assumes that so long 
as the identity of a substance is preserved its molecules remain 
undivided ; but when, by some chemical change, its identity is 
lost, and new substances are formed, the theory supposes that the 
molecules themselves are broken up into still smaller particles, 
which it calls atoms. Indeed it regards this division of the 
molecules as the very essence of a chemical change. 

The word atom is derived from a, privative, and refxvco (I 
cut), and recalls a famous controversy in regard to the infinite 
divisibility of matter, which for many centuries divided the 
philosophers of the world. But chemistry does not deal with 
this metaphysical question. It asserts nothing in regard to the 
possible divisibility of matter ; but its modern theories claim 
that, practically, this division cannot be carried beyond a certain 
extent, and that we then reach particles which cannot be fur- 
ther divided by any chemical process now known. These are 
the chemical atoms, and the atom is simply the unit of the 
chemist, just as the molecule is the unit of the physicist, or the 
stars the units of the astronomer. The molecule is a' group of 
atoms, and is a unit in the microcosm, of which it is a part, in 
the same sense that the solar system is a unit in the great stel- 
lar universe. The molecule has been defined as the smallest 
particle of any substance which can exist by itself, and the 
atom may be now defined as the smallest mass of an element 
that exists in any molecule. 

When a molecule breaks up, it is not supposed that the atoms 
fall apart like grains of sand; but simply that they arrange 
themselves in new groups, and thus give rise to the formation 
of new substances. Indeed, as a rule, the atoms cannot exist 
in a free state, and with few exceptions every molecule consists 
of at least two atoms. This is thought to be true, even of the 
chemical elements. The difference between the molecules of 



ATOMS. 25 

an elementary substance and those of a compound, according 
to the theory, is merely this, that while the first are formed by 
the union of atoms of the same kind, the last comprise atoms 
of different kinds. The molecules of oxygen gas are atomic 
aggregates as well as those of water, only the molecules of 
oxygen consist of oxygen atoms alone, while the molecules of 
water contain both oxygen and hydrogen atoms. Such at least 
is the constitution of most elementary substances. Nevertheless, 
in the case of mercury, zinc, cadmium, and some other me- 
tallic elements, the facts compel us to believe that the molecule 
consists of but one atom, or, in other words, that in these cases 
the molecule and the atom are the same. 

19. Atomic Weights. — There must be evidently as many 
kinds of atoms as there are elementary substances ; and, since 
these substances always unite in definite proportions, it must 
be also true that the elementary atoms have definite weights. 
This once assumed, the law of multiple proportions, as well 
as that of definite proportions, becomes an essential part of our 
atomic theory ; for, since the atoms are by definition indivis- 
ible, the elements can only combine atom by atom, and must 
therefore unite either in the proportion of the atomic weights 
or in some simple multiples of this proportion. We have dis- 
covered no means of measuring even approximately the ab- 
solute weight of an atom ; but, after we have determined, from 
considerations hereafter to be discussed, what must be the num- 
ber of atoms of each kind in one molecule of any substance, 
we can easily calculate their relative weight from the results of 
analysis. A few examples will make the method plain. 

1. The analysis of water, given on page G, proves that in 
100 parts it contains 11.112 parts of hydrogen and 88.888 
parts of oxygen. Every molecule of water, then, must contain 
these two elements in just these proportions. Now we have 
good reason for believing that each molecule of water is a 
group of three atoms, — two of hydrogen and one of oxygen. 
Then, since h (11.112) : 88.888 = 1:16, it follows that the 
oxygen atom must weigh 1G times as much as the hydrogen 
atom ; and, if we make the hydrogen atom the unit of our atom- 
ic weight, then the weight of the oxygen atom, estimated in 
these units, must be 16. 

2. The analysis of hydrochloric acid gas proves that it con- 



26 ATOMS. 

tains in 100 parts 2.74 parts of hydrogen and 97.2G of chlorine. 
Moreover, we have reason to believe that each molecule of the 
acid is a group of two atoms, — one of hydrogen and one of 
chlorine. Hence the atom of chlorine must weigh 35.5 times as 
much as that of hydrogen. Its atomic weight is then 35.5. 

3. The analysis of common salt, page 6, proves that it con- 
tains in 100 parts 60.68 parts of chlorine and 39.32 parts of 
sodium, and we believe that each molecule of salt is a group of 
two atoms, one of chlorine and one of sodium. Then, since 
60.68 : 39.32 == 35.5 : 23, it follows that the atomic weight 
of sodium is 23. In like manner the atomic weights of all the 
chemical elements have been determined, and the numbers are 
given in Table II. These numbers are the fundamental data 
of chemical science, and the basis of almost all the numerical 
calculations which the chemist has to make. The elements of 
a compound body are always united either in the proportions, 
by weight, expressed by these numbers, or else in some simple 
multiples of these proportions ; and whenever, by the breaking 
up of a complex compound, or by the mutual action of different 
substances on each other, the elements rearrange themselves, 
and new compounds are formed, the same numerical propor- 
tions are always preserved. 

The atomic weights evidently rest on two distinct kinds of 
data ; first on the results of chemical analysis, which are facts 
of observation, and in regard to which the only question can be 
as to their greater or less accuracy ; secondly, on our conclu- 
sions in regard to the number of atoms in each molecule of the 
substance analyzed. This conclusion again is based chiefly on 
two classes of facts, whose bearing on the subject we must 
briefly consider. 

]. In the first place we carefully compare together all the 
compounds of the element we are studying, with the view of 
discovering the smallest weight of it which enters into the com- 
position of any known molecule; for this must evidently be the 
atomic weight of the element. An example will make the 
course of reasoning intelligible. 

In the following table we have a list of a number of the 
most important compounds containing hydrogen, all of which 
either are gases, or can easily be changed into vapor by heat, 



ATOMS. 27 

so that their specific gravities in the state of gas can be readily 
determined. From these specific gravities we learn the weights 
of the molecules (compare § 17) which are given in the second 
column of the table. In the third column we have given the 
weight of hydrogen contained in the molecules, referred, of 
course, to the same unit as the weight of the molecules 
themselves : — 



Compounds of Hydrogen. 


Weight of Molecule 

referred to 

Hydrogen Atom. 


Weight of Hydrogen 
in the Molecule. 


Hydrochloric Acid 


36.5 


1 


Hydrobromic Acid 


81.0 


1 


Hydriodic Acid 


128.0 


1 


Hydrocyanic Acid 


27.0 


1 


Hydrogen Gas 


2.0 


2 


Water 


18.0 


2 


Sulphuretted Hydrogen 


34.0 


2 


Seleniuretted Hydrogen 


81.5 


2 


Formic Acid 


46.0 


2 


Ammonia 


17.0 


3 


Phosphu retted Hydrogen 


34.0 


3 


Arseniuretted Hydrogen 


78.0 


3 


Acetic Acid 


60.0 


4 


defiant Gas 


28.0 


4 


Marsh Gas 


16.0 


4 


Alcohol 


46.0 


6 


Ether 


74.0 


10 



Assuming now, as has been assumed in this table, that a 
molecule of hydrogen gas weighs 2, it appears that the 
smallest mass of hydrogen which the molecule of any known 
substance contains, weighs just one half as much, or 1. We 
infer, therefore, that this mass of hydrogen cannot be divided 
by any chemical means, or, in other words, that it is the hydro- 
gen atom. The molecule of hydrogen gas contains then two 
hydrogen atoms, and this atom is the unit to which we refer all 
molecular and atomic weights. 

If now, in like manner, we bring into comparison all the 
volatile compounds of oxygen, we shall find that the smallest 
mass of oxygen which exists in the molecule of any known 
substance weighs 16, — the atom of hydrogen weighing 1, — 
and hence we infer that this mass of oxygen is the oxygen atom. 
Moreover it will appear that a molecule of oxygen gas weighs 



28 ATOMS. 

32, and hence it follows that each molecule of oxygen gas, like 
the molecule of hydrogen, is formed by the union of two. atoms. 
A similar comparison would show that, while the molecule of 
nitrogen gas weighs 28, the atom weighs 14, so that here again 
the molecule consists of two atoms. This method .of investiga- 
tion can be extended to a large number of the chemical ele- 
ments, and the conclusions to which it leads are evidently le- 
gitimate, and cannot be set aside, until it can be shown that 
some substance exists whose molecule contains a smaller mass 
of any element than that hitherto assumed as the atomic weight, 
or, in other words, until the old atom has been divided. 

2. The second class of facts on which we rely for determin- 
ing the number of atoms in a given molecule is based on the 
specific heat of the elements (compare § 16). It would appear 
that the specific heat is the same for all atoms, and, if this is 
true, we might expect that equal amounts of heat would raise 
to the same extent the temperatures of such quantities of the 
various elementary substances as contain the same number of 
atoms, provided, of course, that these atomic aggregates are 
compared under the same conditions. Now we can determine 
accurately the number of units of heat required to raise the 
temperature of equal weights of the elementary substances one 
degree, and the results, which we call the specific heat of the 
elements, are given in works on physics. Chem. Phys. (232). 
Evidently, if our principle is true, these values must be pro- 
portional in every case to the nnmber-ef atoms of each element 
contained in the equal weights compared. Representing then 
by /Sand S' the specific heat of two elementary substances, by 
m and m' the weights of the corresponding atoms, and by unity 
the equal weights compared, we shall have, in any case, 

S:S'= i:i, ovmS=m'S', [HI 

that is, The product of the atomic weight of an elementary sub- 
stance hy its specific heat is always a constant quantity. 

Taking now the atomic weights obtained by the method first 
given, and the specific heats of the elements as they have been 
determined by experimenting on these substances in the solid 
state, we find that, with only three exceptions, our inference is 



ATOMS. 29 

correct ; and this principle not only frequently enables us to fix 
the atomic weight of an element, when the first method fails, 
but it also serves to corroborate the general accuracy of our 
results. It is true, owing undoubtedly to many causes which 
influence the thermal conditions of a solid body, that this prod- 
uct is not absolutely constant. It varies between 5.7 and 6.9, 
the most probable value being very nearly 6.34. But the 
variation is not important, so far as the determination of the 
atomic weights is concerned. This determination, as we have 
seen, rests chiefly on the results of analysis. The question al- 
ways is only between two or three possible hypotheses, and as 
between these the specific heat will decide. For example, an 
analysis of chloride of silver proves that each molecule contains 
for one atom, or 35.5 parts of chlorine, 108 parts of silver. 
Now, 108 parts of silver may represent one, two, three, or four 
atoms, or it may be that this quantity only represents a fraction 
of an atom. To determine, we divide 6.34 by 0.057, the specific 
heat of silver. The result is 111, which, though not the exact 
atomic weight, is near enough to show that 108 is the weight 
of one atom, and not of two or three. The exceptions to this 
rule referred to above are carbon, boron, and silicon. But the 
specific heat of these elements varies so very greatly with 
the differences of physical condition — the so-called allotropic 
modifications — which these elements present, — Chem. Phys. 
(234), — that the exceptions are not regarded as invalidat- 
ing the general principle. The law simply fails in these cases, 
and we can see why it fails. 

This important law, whose bearing on our subject we have 
briefly considered, was first discovered by Dnlong and Petit, and 
was subsequently verified by the very careful experiments of 
llegnault. More recently it has been found, by Voestyn and 
others, that its application extends, in some cases at least, to 
chemical compounds ; for it would seem that the atoms retain, 
even when in combination, their peculiar relations to heat, so 
that the product of the specific heat of a substance by its molec- 
ular weight is equal to as many times 6.3 as there are atoms in 
the molecule. Thus the specific heat of common salt, multiplied 
by its molecular weight, gives 0.214 X 58.5 = 12.52, which is 
very nearly equal to 6.3 X 2 ; while in the case of corrosive 
sublimate the corresponding product, 0.069 X 271 = 18.70, is 



30 ATOMS. 

nearly equal to 6.3 X 3, — results which are in accordance 
with our views in regard to the number of atoms in the mole- 
cules of these substances. 

We have here, then, an obvious method by which we might 
determine the number of atoms in the molecule of any solid, 
and which would be of the very greatest value in investigating 
the atomic weights, could we rely on the general application 
of our law. We do not expect mathematical exactness. We 
know very well that the specific heat of solid bodies varies 
very greatly with the temperature, as well as from other phys- 
ical causes, and that it is impossible to compare them under 
precisely the same conditions, as would be required in order to 
secure accuracy. But, unfortunately, the discrepancies are so 
great, and we are so ignorant of their cause, that as yet we 
have not been able to place much reliance on the specific heat 
as a means of determining the number of atoms in the mole- 
cules of a compound. 

3. Lastly, assuming that both of the means we have consid- 
ered fail to give satisfactory evidence in regard to the number 
of atoms in the molecule of a given substance (which we may 
have analyzed for the purpose of determining some atomic 
weight), we may frequently, nevertheless, reach a satisfactory, 
or at least a probable conclusion, by comparing the substance 
we are investigating with some closely allied substance whose 
constitution is known. Thus, if the molecule of sodic chlo- 
ride (common salt) contains two atoms, it is probable that 
the molecules of sodic iodide, as well as those of potassic 
chloride and potassic iodide, contain the same number ; for 
all these compounds not only have the same crystalline form 
and the same chemical relations, but also they are composed 
of closely allied chemical elements. Nevertheless it is true, in 
very many cases, that our conclusion in regard to the number 
of atoms which a molecule may contain is more or less hypo- 
thetical, and hence liable to error and subject to change. This 
uncertainty, moreover, must extend to the atomic weights of 
the elements, so far as they rest on such hypothetical conclu- 
sions. 

If we change the hypothesis in any case, we shall obtain a 
different atomic weight; but then the new weight will be 



ATOMS. 31 

some simple multiple of the old, and will not alter the impor- 
tant relations to which we first referred. These fundamental 
relations are independent of all hypothesis, and rest on well- 
established laws. 

The atomic weights are the numerical constants of chem- 
istry, and in determining their value it is necessary to take 
that care which their importance demands. The essential part 
of the investigation is the accurate analysis of some compound 
of the element whose atomic weight is sought. The compound 
selected for the purpose must fulfil several conditions. It must 
be one which can be prepared in a condition of absolute purity. 
It must be one the proportions of whose constituents can be 
determined with the greatest accuracy by the known methods 
of analytical chemistry. It must contain a second element 
whose atomic weight is well established. Finally, it should be 
a compound whose molecular condition is known, and it is best 
that this should be as simple as possible. When they are once 
thus accurately determined, the atomic weights become essen- 
tial data in all quantitative analytical investigations. 



Questions and Problems. 

1. Does the integrity of a substance reside in its molecules or in 
its atoms ? 

2. We find by analysis that in 100 parts of potassic chloride 
there are 52.42 parts of potassium and 4 7.58 parts of chlorine. 
Moreover, we know from previous experiments that the atomic 
weight of chlorine is 35.5, and we have reason to believe that every 
molecule of the compound consists of two atoms, one of potassium 
and one of chlorine. What is the atomic weight of potassium ? 

Ans. 39.1. 

3. We find by analysis that in 100 parts of phosphoric anhydride 
there are 43.66 parts of phosphorus and 56.34 parts of oxygen. 
Moreover, we know that the atomic weight of oxygen is 16; and we 
have reason to believe that every molecule of the compound consists 
of seven atoms, 2 of phosphorus and 5 of oxygen. What is the 
atomic weight of phosphorus ? Ans. 31. 

4. In Table III. the student will find the molecular weights of the 
following oxygen compounds; and we give below, following the 
name, the weight of oxygen (estimated like the molecular weight 
in hydrogen atoms) which each contains. From these data it is 



32 ATOMS. 

required to determine the atomic weight of oxygen. Oxygen Gas, 
32; Water, 16; Sulphurous Anhydride, 32, Sulphuric Anhydride, 
48; Phosphoric Oxychloride, 16; Carbonic Oxide, 16 ; Carbonic 
Anhydride, 32 ; Osmic Anhydride, 64 ; Nitrous Oxide, 16 ; Nitric 
Oxide, 16 ; and Nitric Peroxide, 32. Ans. 16. 

5. We give below the weight of chlorine in one molecule of 
several of its most characteristic volatile compounds. It is required 
to deduce the atomic weight of chlorine on the principle of the last 
problem. Chlorine gas, 71; Phosphorous Chloride, 106.5; Phos- 
phoric Oxychloride, 106.5; Arsenious Chloride, 106.5; Phosgene 
Gas, 71 ; Stannic Chloride, 142 ; Stanno-triethylic Chloride, 35.5 ; 
and Hydrochloric Acid, 35.5. Ans. 35.5. 

6. Review the steps of the reasoning by which the atomic weights 
have been deduced in the last two problems, and show that the 
" molecular weight " and " the weight of the element in one molecule " 
are actual and independent experimental data. 

7. Analysis shows that in 100 parts of mercuric chloride there are 
73.80 parts of mercury and 26.20 parts of chlorine. The specific 
heat of mercury is 0.032. What is the probable atomic weight of 
mercury, that of chlorine being 35.5 ? Also, how many atoms of 
each element does one molecule of the compound contain ? 

Ans. Atomic weight of mercury, 200. Each molecule consists 
of one atom of mercury and two of chlorine. 

8. Analysis shows that in 100 parts of ferric oxide there are 70 
parts of iron and 30 parts of oxygen. The specific heat of iron is 
0.114. What is the probable atomic weight of iron, that of oxygen 
being 16 ? and also, how many atoms of each element does one 
molecule of the oxide contain ? 

Ans. Atomic weight of iron, 56. One molecule of ferric oxide 
contains 2 atoms of iron and 3 of oxygen. 

9. The molecular weight of silicic chloride is 1 70, and its specific 
heat, 0.1907. How many atoms does one molecule of the compound 
probably contain ? Ans. 5. 

10. The molecular weight of mercuric iodide is 454, and its 
specific heat, 0.042. How many atoms does one molecule of the 
compound probably contain ? Ans. 3. 



CHAPTER V. 

CHEMICAL NOTATION. 

20. Chemical Symbols. — The atomic theory has found ex- 
pression in chemistry in a remarkable system of notation, which 
has been of the greatest value in the study of the science. Jn 
this system, the initial letter of the Latin name of an element 
is used as the symbol of that element, and represents in every 
case one atom. Thus stands for one atom of Oxygen, iVfor 
one atom of Nitrogen, H for one atom of Hydrogen. "When 
several names have the same initial, we add for the sake of dis- 
tinction a second letter. Thus C stands for one atom of Car- 
bon, CI for one atom of Chlorine, Ca for one atom of Calcium, 
Cu for one atom of Cuprum (copper), Cr for one atom of 
Chromium, Co for one atom of Cobalt, Cd for one atom of 
Cadmium, Cs for one atom of Caesium, and Ce for one atom 
of Cerium. The symbols of all the elements are given in 
Table II. Several atoms of the same element are generally 
indicated by adding figures, but distinguishing them from alge- 
braic exponents by placing them below the letters. Thus Sn. z 
stands for two atoms of Stannum (tin), jS^ for three atoms 
of Sulphur, and I 5 for five atoms of Iodine. Sometimes, how- 
ever, in order to indicate certain relations, we repeat the symbol 
with or without a dash between them, thus H-II represents a 
group of two atoms of Hydrogen, Se=Se a group of two atoms 
of Selenium. We can now easily express the constitution of 
the molecule of any substance by simply grouping together the 
symbols of the atoms of which the molecule consists. This 
group is generally called the symbol of the substance, and 
stands in every case for one molecule. Thus NaCl is the sym- 
bol of common salt, and represents one molecule of salt. H t O 
is the symbol of water, and represents, as before, one molecule. 
So in like manner H^N stands for one molecule of ammonia 
gas, H 4 C for one molecule of marsh gas, KN0 3 for one mole- 
cule of saltpetre, H.SO^ for one molecule of sulphuric acid, 
3 



34 CHEMICAL NOTATION. 

C 2 H±0 2 for one molecule of acetic acid, H-H for one 
molecule of hydrogen gas. We do not, however, always 
write the symbols in a linear form, but group the letters in such 
a way as will best indicate the relations we are studying. 
When several molecules of the same substance take part in a 
chemical change, we represent the fact by writing a numerical 
coefficient before the molecular symbol. A figure so placed 
always multiplies the whole symbol. Thus 4U-NO s stands 
for four molecules of nitric acid, 3C 2 B 6 for three molecules 
of alcohol, 6 0=0 for six molecules of oxygen gas. When 
clearness requires it, we enclose the symbol of the molecule in 
parentheses, thus, A(H.fN), or (RfN) 4 . The precise mean- 
ing of the dashes will hereafter appear. They are used, like 
punctuation marks, to point off the parts of a molecular sym- 
bol, between which we wish to distinguish. 

21. Chemical Reactions. — These chemical symbols give at 
once a simple means of representing ail chemical changes. As 
these changes almost invariably result from the reaction of one 
substance on another, they are called Chemical Reactions. Such 
reactions must necessarily take place between molecules, and 
simply consist in the breaking up of the molecules and the rear- 
rangement of the atoms in new groups. In every chemical re- 
action w r e must distinguish between the substances which are 
involved in the change and those which are produced by it. 
The first will be termed the factors and the last the products of 
the reaction. As matter is indestructible, it follows that The 
sum of the weights of the products of any reaction must always 
he equal to the sum of the weights of the factors, and, further, 
that The number of atoms of each element in the products must 
be the same as the number of atoms of the same kind in the 
factors. This statement seems at first sight to be contradicted 
by experience, since wood and many other combustibles are 
consumed by burning. In all such cases, however, the apparent 
annihilation of the substance arises from the fact that the prod- 
ucts of the change are invisible gases ; and, when these are col- 
lected, their weight is found to be equal, not only to that of the 
substance, but also, in addition, to the weight of the oxygen from 
the air consumed in the process. As the products and factors 
of every chemical change must be equal, it follows that A 
chemical reaction may always be represented in an equation 



CHEMICAL NOTATION. 35 

by writing the symbols of the factors in the first member and 
those of the products in the second. Thus, the following equa- 
tion expresses the reaction of dilute sulphuric acid on zinc, by 
which hydrogen gas is commonly prepared. The products are 
a solution of zinc sulphate and hydrogen gas. 

Xn + {H,SO, + Aq) = (ZnSOt + Aq) + m-m. [12] 

The initial letters of the Latin word Aqua are here used 
simply to indicate that the substances enclosed with it in pa- 
rentheses are in solution. The symbol Zll is printed in " full- 
faced " type to indicate that the metal is used in the reac- 
tion in its well-known solid condition ; while the symbol of 
the molecule of hydrogen is printed in skeleton type to indi- 
cate the condition of gas. This usage will be followed through- 
out the book; but, generally, when it is not important to indicate 
the condition of the materials involved in the reaction, ordinary 
type will be used. The molecule of hydrogen gas consists of 
two atoms, as our reaction indicates, and this is the smallest 
quantity of hydrogen which can either enter into or be formed 
by a chemical change. The molecule of zinc is known to 
consist of only one atom. When the molecular constitution 
of an element is not known, we simply write the atomic symbol 
in the reaction. 

Among chemical reactions we may distinguish at least three 
classes. First, Analytical Reactions, in which a complex mole- 
cule is broken up into simpler ones. Thus, when sodic bisul- 
phate is heated, it breaks up into sodic sulphate and sulphuric 
anhydride, — 

Na,S,0 7 = tfa,S0 4 + SO,. [13] 

So, also, by fermentation grape sugar or glucose breaks up into 
alcohol and carbonic anhydride, — 

C 6 H l2 0, = 2 CM 6 + 2 CO* [14] 

Secondly, Synthetical Reactions, in which two molecules 
unite to form a more complex group. Thus baryta burns 
in an atmosphere of sulphuric anhydride, and forms baric 
sulphate, — 

BaO+ S0 3 = BaSO r [15] 



36 CHEMICAL NOTATION. 

In like manner ammonia enters into direct union with hydro- 
chloric acid to form ammonic chloride, — ■ 

%& + BCl==z HJfCl [1 6] 

Thirdly, Metathetical Reactions, in which the atoms of one 
molecule change place with the dissimilar atoms of another, 
one atom of one molecule replacing one, two, three, or more 
atoms of the other, as the case may be. Thus, when we add a 
solution of common salt to a solution of argentic nitrate, we ob- 
tain a white precipitate 1 of argentic chloride, while sodic nitrate 
remains in solution. The result is obtained by a simple in- 
terchange between an atom of silver and an atom of sodium, 
as the following reaction shows : — 

(JVaa+ AgNOz + Aq) = (NaNO s + Aq) + AgCL [17] 

In the next example, one atom of barium changes place with 
two atoms of hydrogen. Baric chloride and sulphuric acid 
yield hydrochloric acid and insoluble baric sulphate, which is 
precipitated from the solution in water as the reaction in- 
dicates, — 

(BaCI 2 + B 2 S0 4 + Aq) = (2HCI + Aq) + RaS0 4 [18] 

Of the three classes of chemical reactions the last is by far 
the most common, and many chemical changes which were for- 
merly supposed to be examples of simple analysis or synthesis 
are now known to be the results of metathesis. In very many 
cases, however, a chemical reaction cannot be explained in 
either of these ways alone, but seems to consist in a primary 
union of two or more molecules and a subsequent splitting up 
of this large group. Indeed, this is the best way of conceiving 
of all metathetical reactions, for we do not suppose that in any 
case there is an actual transfer of atoms from one molecule to 
the other. The word metathesis is merely used to indicate the 
result of the process, not the manner in which the change takes 
place, and the same is true of the words analysis and synthesis. 

1 The separation of a solid or sometimes of a liquid substance in a fluid 
menstruum, as the result of a chemical reaction, is called precipitation, and 
the material which separates, a precipitate; and this, too, even when the ma- 
terial, being lighter than the fluid, rises instead of falls. 



CHEMICAL NOTATION. 37 

The common method of preparing carbonic anhydride is to 
pour a solution of hydrochloric acid on small lumps of marble 
(calcic carbonate), — 

CaCO s + {2HCI + Aq) = (CaC0 3 H..CI, + [19] 
Aq) = ( Ca CL 2 + B i O + Aq)+ @© 2 . 

We may suppose that the molecules of the two substances are, 
in the first place, drawn together by the force which manifests 
itself in the phenomena of adhesion, 1 but that, as they approach, 
a mutual attraction between their respective atoms comes into 
play, which, the moment the molecules come into collision, 
causes the atoms to arrange themselves in new groups. The 
groups which then result are determined by many causes 
whose action can seldom be fully traced ; but there are two 
conditions which, when the substances are in solution, have a 
very important influence on the result. These conditions may 
be thus stated : — 

1. Whenever a compound can be formed, which is insoluble 
in the menstruum present, this compound always separates as 
a precipitate. 

2. Whenever a gas can be formed, or any substance which 
is volatile at the temperature at which the experiment is made, 
this volatile product is set free. 

The reactions 17 and 18 of this section are examples of 
the first, while the reactions 12 and 19 are examples of the 
second of these conditions. The facts just stated illustrate 
an important truth, which must be carefully borne in mind in 
the study of chemistry. A chemical equation differs essen- 
tially from an algebraic expression. Any inference which 
can be legitimately drawn from an algebraic equation must, in 
some sense, be true. It is not so, however, with chemical sym- 
bols. These are simply expressions of observed facts, and, 
although important inferences may sometimes be drawn from 
the mere form of the expression, yet they are of no value 
whatever unless confirmed by experiment. Moreover, the facts 

1 "We find it convenient to distinguish between the force which holds to- 
gether different molecules and that which unites the atoms of the molecules. 
To the last we give the name of chemical affinity, while we call the first co- 
hesion or adhesion, according as it is exerted between molecules of the same 
kind or those of a different kind. 



38 CHEMICAL NOTATION. 

which are expressed in this peculiar system of notation are 
as purely materials for the memory as if they were described 
in common language. 

22. Compound Radicals. — In many chemical reactions the 
elementary atoms change places, not with other elementary 
atoms, but with groups of atoms, which appear to sustain rela- 
tions to the compounds they leave or enter similar to those of 
the elements themselves. Thus, if we add to a solution of ar- 
gentic nitrate a solution of amnionic chloride, we get the reac- 
tion expressed by the equation 

AgNO, + NH± CI = NH.-NO, + Ag CI [20] 

Here the group NH± has taken the place of Ag. So, also, 
in the reaction of hydrochloric acid on common alcohol, the 
group C 2 B 5 in the molecule of alcohol changes places with the 
atom of hydrogen in the molecule of hydrochloric acid, — 

C t H :7 0-H-\- HCl = H-0-H+ C,H.jCl. [21] 

Alcohol. EthyUc Chloride. 

"We write the symbols in this peculiar way in order to make 
it evident to the eye that such a substitution has taken place. 
Lastly, in the reaction of chloroform on ammonia, the group 
CH of the first changes places with the three atoms of hydro- 
gen of ammonia gas, — 

cm ci s + ir^= bhci + cmK [22] 

Chloroform. Hydrocyanic Acid. 

Such groups as these are called compound radicals. Like 
the atoms themselves, they cannot, as a rule, exist in a free 
state ; but aggregates of these radicals may exist, which sus- 
tain the same relation to the radicals that elementary substances 
hold to the atoms. Thus, as we have a gas chlorine consisting 
of molecules, represented by Cl-Cl, so there is a gas cyanogen 
consisting of molecules, represented by CN-CN , where CiVis 
a compound radical called cyanogen. Again, the important 
radicals CO, S0 2 , and PCl 3 , are also the molecules of well- 
known gases. These radical substances correspond to the ele- 
mentary substances previously mentioned, in which the mole- 
cule is a single atom. 

But with few exceptions the radical substances have never 



CHEMICAL NOTATION. 39 

been isolated, and the radicals are only known as groups of 
atoms which pass and repass in a number of chemical reac- 
tions. Indeed, in the same compound we may frequently 
assume several radicals. The possible radicals of a chemi- 
cal symbol correspond in fact almost precisely to the possi- 
ble factors of an algebraic formula, and in writing the sym- 
bol we take out the one or the other, as the chemical change 
we are studying requires. A number of these radicals have 
received names, and among those recognized in mineral com- 
pounds a few of the most important are 

Hydroxy 1 II Sulpburyl S0 t 

Hydrosulphuryl IIS Carbonyl CO 

Ammonium I^N Phosphoryl PO 

Amidogen II „N Nitrosyl NO 

Cyanogen CN Nitryl N0 3 . 

The radicals recognized in organic compounds are very 
numerous, and will be tabulated hereafter. 






Questions mid Problems. 

1. For what do the following symbols stand ? 

JV; Car, HH; H,C; 4BJYO,; (C,H±0.^. 

2. For what do the following symbols stand ? 

CI; S 3 ; 0-0; II,N; H,SO, ; SCM.O. 

3. For what do the following symbols stand ? 

0; B 5 ; Se-Se; NaCl\ H,0 ; ZKNO z . 

4. Analyze the following reaction. Show that the same number 
of atoms are represented on each side of the equation, and state the 
class to which it belongs. 

Fe + {'2HCI + Aq) = (FeCI, + Aq) + HHH. 

Hydrochloric Acid Ferrous Chloride. 

5. Analyze the following reaction. Show in what the equality 
consists, and state the class to which the reaction belongs. 

N,H,0, = '2H,0 + N,0. 

Amnionic Nitrate. Water." Nitrous Oxide. 

6. Analyze the following reaction. Show in what the equality 
consists, and state the class to which the reaction belongs. 

C+ 0-0 = CO., 

Carbon. Oxygen. Carbonic Anhydride. 



40 CHEMICAL NOTATION. 

7. Analyze the following reaction. Show in what the equality- 
consists, and state the class to which the reaction belongs. 

2H-0-H+ Na-Na = 2Na-0-H+ H-H. 

Water. Sodium. Sodic Hydrate. 

8. The following reaction may be so written as to indicate that 
the products are formed by a metathesis between two similar mole- 
cules. It is required to show that this is possible. 

2HzN = ZH-H + N-K 

Ammonia gas. Hydrogen gas. Nitrogen gas. 

9. Write the reactions [17] and [18] so as to indicate the manner 
in which the metathesis is supposed to take place. 

10. State the conditions which determine the metathesis in the 
various reactions given in this chapter so far as these conditions are 
indicated. 

11. Write the reactions [21] and [22] so as to indicate the manner 
in which the metathesis is supposed to take place. 

12. Analyze the following reaction. Show what determines the 
metathesis and also what is meant by a compound radical. 

(Pb-(NO s ) 2 + 2NH A -Cl+Aq) = 

Plumbic Nitrate. Ammonic Chloride. 

Pb€I 2 + (2Nff 4 -NO s + Aq) 

Plumbic Chloride. Ammonic Nitrate. 

13. Compare with [22] the following reaction and point out the 
two radicals, which, as we may assume, hydrocyanic acid contains. 

{Ag-NO, + R-CJST+ Aq) = Ag-fm + {H-NO, + Aq) 

Argentic Nitrate. Hydrocyanic Acid. Argentic Cyanide. Nitric Acid. 

14. When sulphuric anhydride (SO s ) is added to water (H 2 0) a 
violent action ensues and sulphuric acid is formed. The reaction 
may be written in two ways, and it is required to explain the different 
views of the process, which the following equations express. 

H 2 + SO z =^H 2 SO± 

or 2R-0-B+ SO.fO = R 2 =0,=S0 2 + H 2 =0. 

15. State the distinction between a chemical element and an 
elementary substance. Give also the distinction between a com- 
pound radical and a radical substance. 

16. Give the names of the following radicals. 

MO; US; NH A \ NH 2 i S0 2 ; CO; PO; N0 2 . 




CHAPTER VI. 



STOCHIOMETRY. 



23. Stochiometry. — The chemical symbols enable us not 
only to represent chemical changes, but also to calculate ex- 
actly the amounts of the substances required in any given pro- 
cess as well as the amounts of the products which it will yield. 
Each symbol stands for a definite weight of the element it rep- 
resents, that is, for the weight of an atom ; but, as only the rela- 
tive values of these weights are known, they are best expressed 
as so many parts. Thus H stands for 1 part by weight of 
hydrogen, the unit of our system. In like manner stands 
for 16 parts by weight of oxygen, N for 14 parts by weight 
of nitrogen, C for 12 parts by weight of carbon, C 3 for 60 parts 
by weight of carbon, and so on for all the symbols in Table II. 
The weight of the molecule of any substance must evidently 
be the sum of the weights of its atoms, and is easily found, 
when the symbol is given, by simply adding together the 
weights which the atomic symbols represent. Thus H.,0 
stands for 2 + 16= 18 parts of water, H^N 'for 3 + 14 = 17 
parts of ammonia gas, and C 2 H^0 2 for 24 — |— 4 — [— 32 = 60 
parts of acetic acid. 1 

Having then given the symbol of a substance, it is very easy 
to calculate its percentage composition. Thus, as in 60 parts of 
acetic acid there are 24 parts of carbon, in 100 parts of the 
acid there must be 40 parts of carbon, and so for each of the 
other elements. The result appears below ; and in the same 
way the percentage composition both of alcohol and ether has 
been calculated from the accompanying symbol. 

1 In this book " the molecular weight of a substance " will always mean the 
sum of the atomic weights of the atoms composing one molecule, and we shall 
use the phrase, " the molecular weight of a symbol" or " the total atomic weight 
of a symbol," to denote the sum of the atomic weights of all the molecules which 
the symbol represents. 



42 





STOCHIOMETRY. 






Acetic Acid Alcohol 


Ether 




C^H^. C 2 H 6 0. 


CtH 10 O. 


Carbon 


40.00 52.18 


64".86 


Hydrogen 


6.67 13.04 


13.52 


Oxygen 


53.33 34.78 


21.62 



100.00 100.00 100.00 

The rule, easily deduced, is tins : As the weight of the mole- 
cule is to the weight of each element, so is one hundred parts to 
the percentage required. 

On the other hand, having given the percentage composition, 
it is easy to calculate the number of atoms of each element in 
the molecule of the substance. This problem is evidently the 
reverse of the last, but it does not, like that, always admit of a 
definite solution ; for, while there is but one percentage compo- 
sition corresponding to a given symbol, there may be an infinite 
number of symbols corresponding to a given percentage com- 
position. For example, the percentage composition of acetic 
acid corresponds not only to the formula C. 2 H A 2% given above, 
but also to any multiple of that formula, as can easily be seen 
by calculating the percentage composition of CJI 2 0, C 3 H 6 3 , 
C±H & Ov &c. They will all necessarily give the same result, 
and, before we can determine the absolute number of atoms of 
each element present, we must have given another condition, 
namely, the sum of the weights of the atoms, or, in other 
words, the molecular weight of the substance. When this is 
known, the problem can at once be definitely solved. 

Suppose we have given the percentage composition of alco- 
hol, as above, and also the further fact that its molecular weight 
is 46. We can then at once make the proportion 

100 : 52.1 8 = 46 : x = 24 the weight of the atoms of carbon, 
100: 13.04 = 46 : x = 6 " " " " " ''hydrogen, 
100:34.78 = 46:^=16 " " " " " "oxygen. 

Then it follows that 
2- j = 2 the number of atoms of carbon in one molecule, 
6. _ g « a a « « hydrogen in one molecule, 

-is — 1 " « " " " oxygen in one molecule. 

It is evident from this example, that, in order to determine 



STOCHIOMETRY. 43 

exactly the symbol of a compound, we must know its molecular 
weight. "When the substance is a gas, or is capable of being 
changed into vapor, we can easily ^determine its molecular 
weight by the principle on page 18. If The molecular weight is 
simply twice its specific gravity referred to hydrogen./ For all 
the problems given in this book, which deal only with the com- 
mon ga>es and vapors, the molecular weight can be at once 
taken from Table III. If we are dealing with a new substance, 
we must determine its specific gravity experimentally by one of 
the methods which will hereafter be described. 

When, on account of the fixed nature of the substance, the 
last mode of investigation is impossible, we can still frequently 
determine with great probability the molecular weight, by study- 
ing the chemical reactions into which the substance enters, and 
connecting, by careful quantitative experiments, the molecular 
weight sought with that of some substance whose molecular 
weight is known. The methods used in such cases will be in- 
dicated hereafter ; but even when all such means fail, we can 
nevertheless always find which of all possible symbols ex- 
presses the composition of the substance we are studying in 
the simplest terms, in other words, with the fewest number of 
atoms in the molecule. Suppose the substance to be cane sugar, 
which cannot be volatilized without decomposition, and of which 
no reaction is known which gives any definite clew to its mole- 
cular weight. Peligot's analysis, cited on page 9, shows that it 
contains, in 100 parts, 42.06 parts of carbon, 6.50 parts of 
hydrogen, and 51.44 parts of oxygen. Assume for the mo- 
ment that the molecular weight is equal to 100 then 

42.06 

-— - — 3.50 the number of atoms of carbon. 

~ = 6.50 « " « " " hydrogen. 

51 44 

- ig -=3.22 " « " " " oxygen. 

This would be the number of atoms of each element if the 
sum of the atomic weight, that is, the molecular weight, of 
sugar, were equal to 100. As, from the very definition, frac- 
tional atoms cannot exist, these numbers are impossible, but 
any other possible number of atoms must be either a multiple 
or a submultiple of the numbers found ; and we can easily dis- 



44 STOCHIOMETRY. 

cover the fewest number of whole atoms possible, by seeking for 
the three smallest whole numbers which stand to each other 
in the relation of 3.50 : G.50 : 3.22, a proportion which is very 
nearly satisfied by 12 : 22 : 11. Hence, the simplest possible 
symbol is C 12 H. 22 O n , and this has been adopted by chemists as 
the symbol of cane sugar, although, from anything we as yet 
know, the symbol may be a multiple of this. If now, taking 
this symbol as our starting-point, we calculate the percentage 
composition which would exactly correspond to it, we obtain 
the following results, which we have arranged in a tabular 
form, so that the student may compare the theoretical compo- 
sition with the numbers Peligot obtained by actual analysis. 



Composition of Cane 

L/]o -"22 ^11 • 


Sugar, 


Carbon 


Peligot's Analysis. 
42.06 


Theoretical. 
42.11 


Hydrogen 
Oxygen 


6.50 
51.44 


6.43 
5J. 46 



100.00 100.00 

The difference between the two is now seen to be within the 
probable errors of analysis, and this example illustrates the 
method of arranging analytical results generally adopted by 
chemists. 

From the above discussion we can easily deduce a simple 
arithmetical rule for finding the symbol of a compound when 
its percentage composition is known. But this rule may be best 
expressed in an algebraic formula, which will show to the eye 
at once the relation of the quantities involved in the calcula- 
tion, and enable us to extend our method to the solution of 
many classes of problems which we might not otherwise foresee. 
Let us then represent 

By M the weight of any chemical compound in grammes. 
" m the molecular weight of the compound in hydrogen 

atoms. 
" W the weight of any constituent of that compound, whether 

element or compound radical, in grammes. 
" w the total atomic weight of element or radical in one 

molecule. 



STOCHIOMETEY. 45 



= proportion by weight of the constituent in the compound, 



Then 
w 
m 
and 

M — = weight of constituent in M grammes of compound, or 

W=M-. P231 

m L J 

Any three of these quantities being given, the fourth can, of 
course, be found. Thus we may solve four classes of problems. 

1. We may find the weight of any constituent in a given 
weight of a compound, when we know the molecular weight of 
the compound and the total atomic weight of the constituent in 
one molecule. 

Problem. It is required to find the weight of sulphuric 
^<\ anhydride S0 3 in 4 grammes of plumbic sulphate PbO, S0 3 . 
Here, to = 32 + 3 X 16 = 80, ™ = 207 + 16 + 80 = 303, 
and Af = 4. Ans. 1.056 grammes. 

2. We can find the weight of a compound which can be 
produced from, or corresponds to, a given weight of one of its 
constituents, when the same quantities are known as above. 

Problem. How many grammes of crystallized green vitriol, 
FeS0 4 . 711,0, can be made from 5 grammes of iron? Here, 
w = 56, m = 278, W= 5. Ans. 24.821. 

3. We can find the molecular weight of a compound when 
we have given the weight of one constituent in a given weight 
of the compound, and the total atomic weight of that constitu- 
ent in the molecule. 

Problem. In 7.5 grammes of ethylic iodide, there are 6.106 
grammes of iodine ; the total atomic weight of iodine in one 
molecule is 127. What is the molecular weight of ethylic 
iodide ? - Ans. 156. 

4. We can find the total atomic weight of one constituent of 
a molecule when the molecular weight is "iven, and also the 
weight of the constituent in a known weight of the compound. 



r 

V 



46 STOCHIOMETRY. 

Problem. The molecular weight of acetic acid is 60, the 
per cent of carbon in the compound 40. What is the total 
atomic weight of carbon in one molecule ? Ans. 24. 
Whence number of carbon atoms in one molecule, 2. 

The last problem is essentially the same as that of finding 
the symbol of a compound when its percentage composition is 
given, while the first corresponds to the reverse problem of 
deducing the percentage composition from the symbol. By a 
slight change the formula can be much better adapted to this 
class of cases. For this purpose we may put M = 1 00, since 
we are solely dealing with per cents, and also put w r== na 9 
a standing for the atomic weight of any element, and n for the 
number of atoms of that element in one molecule of the 
compound we are studying. We then have 

W= 100 — and * = ^ - - [24] 

m 100 a L J 

The first of these forms is adapted for calculating the per cent 
of each element of a compound when the molecular weight, 
the number of atoms of each element in one molecule, and the 
several atomic weights, are known ; and it is evident that all 
these data are given by the chemical symbol of the compound. 
The second of these forms enables us to calculate the number 
of atoms of each element present in one molecule of a com- 
pound when the percentage composition, the molecular weight, 
and the several atomic weights, are known, and illustrates the 
principle before developed, that the molecular weight is an 
essential element of the problem. 

24. Stochlometrical Problems. — The principles of the pre- 
vious section apply not only to single molecular formulas, but 
obviously may also be extended to the equations which repre- 
sent chemical changes. Since the molecular symbols which 
are equated in these expressions represent known relative 
weights, it must be true in every case that we can calculate the 
weight of either of the factors or products of the chemical 
change it represents, provided only that the weight of some one 
is known. If w r e represent by w and m the total atomic weight 
of any two symbols entering into the chemical equations, and 
by W and M the weight in grammes of the factors or products 



STOCHIOMETRY. 47 

which these symbols represent, then the simple algebraic 
formulas of the last section will apply to all stochiometrical 
problems of this kind, as well as to those before indicated. 
These formulae, however, are merely the algebraic expression 
of the familiar rule of three, and all stochiometrical problem^ 
are solved more easily by this simple arithmetical rule. Usin^ 
the word symbol to express the sum of the atomic weights it 
represents, we may state the rule as applied to chemical prob- 
lems in the following words, which should be committed to 
memory. 

Express the reaction in the form of an equation ; make then 
the proportion, As the symbol of the substance given is to the sym- 
bol of the substance required, so is the weight of the substance 
given to x, the weight of the substance required ; reduce the 
symbols to numbers, and calculate the value of x. 

This rule applies equally well to all problems, like those of 
the last section, in which the elements or radicals of the same 
molecular symbol are alone involved ; only in such cases there 
is of course no equation to be written. A few examples will 
illustrate the application of the rule. 

Problem 1. We have given 10 kilogrammes of common salt, 
and it is required to calculate how much hydrochloric acid gas 
can be obtained from it by treating with sulphuric acid. The 
reaction is expressed by the equation 

(2Na CI + ILSO, + Aq) = {Na. 2 SO, + Aq) + 21110/, 
whence we deduce the following proportion, 

2NaCl:2NCl= 10 : x = Ans. G.239 kilogrammes. 

Problem 2. It is required to calculate how much sulphuric 
acid and nitre must be used to make 250 grammes of the 
strongest nitric acid. The reaction is expressed by the 
equation 

KJSTO, + H 2 SO, = K, BS0 4 + HNO,, 
whence we got the proportions 

fTS OS 

HN0 3 : M,S0 4 = 250 :x = Ans. 1. 388.9 grammes sulphuric 
acid. 

88 loi.i 

HNOz : KNO z = 250 : x = Ans. 2. 401.2 grammes nitre. 



48 



STOCHIOMETRY. 




The student should also solve by the same rule the problems 

ven in the last section. 

25. Gay-Lussac's Law. — This eminent French chemist was 

e first to state clearly the important truth, that, when gases or 
vapors react on each other, the volumes both of the factors and 
of the products of the reaction always bear to each other some 
very simple numerical ratio. This truth is generally known as 
the law of Gay-Lussac, but, since the principle is a direct con- 
sequence of the atomic theory, it is best studied in that relation. 
It is, as we have seen, a fundamental postulate of the theory that 
equal volumes of all substances, when in the aeriform condition, 
contain the same number of molecules. Hence it follows, that 
the volumes of all single molecules are the same, and, if we take 
this common volume as our unit of measure, it follows, further, 
that the total molecular volume represented by any symbol is 
always equal to the number of molecules. We are thus led to 
a most important fact, which gives an additional meaning to our 
chemical symbols, for it appears that Every chemical equation, 
when properly written, represents not only the relative weights, 
hut also the relative volumes of its factors and products, when in 
the state of gas. 

This principle is illustrated by the following equations : 





CB 4 




+ 2 


0-0 




= 


co 2 


+ 2 


H 2 




A 


larsh G; 


is. 


02 


:ygen G 


as. 


Carbo 


nic Anh 


ydride. Aqt 


eous Va 


per. 


2 


NO 




+ 5 


H-H 




= 2 


NH Z 


+ 2 


H,0 




itr 


ic Oxide 


Gas 


Hy 


drogen 


Gas. 


An 


imonia 


Gas. Aqu 


eous Va 


por. 



The squares which here serve to indicate equal volumes, 
and to impress on the mind the meaning of the symbols, are 
evidently unnecessary and will not be used hereafter. 

The important rule of the last section may be expressed by 
the following proportion 

nm:n'm'=: W: F'=W:W 
Here m and m' represent the molecular weights of any two 
substances, n and n' the number of molecules of these sub- 



STOCHIOMETRY. 49 

stances, which take part in a chemical reaction whether as 
factors or products, while n m and n' m' represent what in the 
statement of our rule we have called the symbols of the sub- 
stances, and the equation expresses the fact that the sum of 
the atomic weights indicated by the symbols is proportional 
to the weights of the substances involved in the chemical reac- 
tion, whether these weights are estimated in grammes or in 
criths (2). 

Now by (17) m' = 2 Sp. Gr. and by [3] TV' = V X Sp. Gr. 

Making these substitutions we may reduce the above propor- 
tion to the following form 

J-n m : n' = TV : V 

and this gives us another stochiometrical rule, by which we can 
calculate the volume of a gas or vapor involved in a chemical 
reaction, when the weight of some other factor or product is 
known, or inversely, when the volume is given calculate the 
weight. 

Express the reaction in an equation ; make then the propor- 
tion, As one half of the symbol of the first substance is to the 
number of molecules of the second, so is the weight in criths of 
the first to the volume in litres of the second ; reduce the symbol 
to numbers, and calculate the value of the unknown quantity. 

This rule has the same general application as the first, and 
a few examples will illustrate the use of it. 

Problem 1. How much chlorate of potash must be used to 
obtain one litre of oxygen gas ? The reaction is expressed by 
the equation 

2KC10 3 =z2KCl+ 3 O-O, 



whence we get the proportion 

122.6 

}(2KClO s ):B=x:l. x = 40.9 criths, 

40.9 X 0.0896 = Ans. 3.664 grammes. 

Problem 2. How many litres of oxygen gas can be obtained 
from 500 grammes of chlorate of potash ? The reaction is the 
same as before, but in this case the grammes must first be 
reduced to criths. The proportion will then be written 
4 



50 STOCHIOMETRY. 

122.6 KQO 

XCl0 3 :3=-^-:x = Ans. 136.6 litres. 
0.0896 

In applying the rules of this chapter to the solving of 
stochiometrical problems, the student should carefully bear in 
mind, first, that the rule of (24) applies to all those cases in 
which the iveiyht of one substance is to be calculated from the 
weight of another ; secondly, that when volume is to be deduced 
from volume the answer can be found by mere inspection of 
the equation according to the principles stated in (25), and 
thirdly, that the rule of page 49 applies only to those problems 
in which volume is to be calculated from weight, or the reverse. 
In using this last rule it must be remembered that the " first 
substance " is always the one whose weiyht is given or sought, 
while the " second substance " is always the one whose volume 
is given or sought. 

Moreover, the student will notice that the volume of any 
aeriform factor or product may also be found by dividing its 
weight in grammes, — calculated by the rule of (24), — by the 
known weight of one litre of the gas or vapor, found from 
Table III. by [3 J 



Questions and Problems. 

1. What is the molecular weight of plumbic sulphate, Pb=0 2 =S0 2 7 
Of calcic phosphate, Ca s W 6 i(PO) 2 ? Of ammonia alum, 
(NHX [;l/ 2 ]|0 8 t(SO,) 4 . 2UI 2 0? Ans. 303, 310, and 906.8. 

2. What are the molecular weights of the symbols 

3C 2 H 4 2 ; 5{FeS0 4 . 1H 2 G) and 7K 2 =0 2 =CO? 

Ans. 180, 1390, and 967.4. 

3. Are the total atomic weights of the two members of the follow- 
ing reaction equal ? 

Fe + (H 2 SO, + Aq) = (FeSO, + Aq) + H-H. 

Ans. The total weight of each member of the equation is 154. 

4. Calculate the percentage composition of ammonic chloride, 
NHfil. Ans. Nitrogen, 26.17; Hydrogen, 7.48; Chlorine, 66.35. 

5. Calculate the percentage composition of nitrobenzole, C 6 H 5 NO z . 
Ans. Carbon, 58.53; Hydrogen, 4.07 ; Nitrogen, 11.39 ; Oxygen, 

26.01. 



STOCHIOMETRY. 51 

6. Given the percentage composition of chloroform as follows : 
Carbon, 10.04 ; Hydrogen, 0.83 ; Chlorine, 89.13. Required the 
symbol, knowing that the Sp. Gr. of chloroform vapor equals 59.75. 

Ans. CHCl r 

7. Given the percentage composition of stanno-diethylic bromide 
as follows: Tin, 35.13; Carbon, 14.29 ; Hydrogen, 2.97 ; Bromine, 
47.61. Required the symbols, knowing that the Sp. Gr. of the 
vapor equals 1G 8. Ans. &nC 4 #i Br 2 . 

8. Given the percentage composition of ethylene chloride as fol- 
lows : Carbon, 21.24 ; Hydrogen, 4.04 ; Chlorine, 71.72. Required 
the symbol, knowing that the Sp. Gr. of the vapor equals 49.5. 

Ans. QH^Ck. 

9. Given the percentage composition of cream of tartar as fol- 
lows: Potassium, 20.79; Hydrogen, 2.66; Carbon, 25.52; Oxygen, 
51.03. Required the simplest symbol possible. Ans. KH.JJ^O^ 

10. Given the percentage composition of crystallized ferrous sul- 
phate as follows: Iron, 20.15; Sulphur, 11.51; Oxygen, 23.02; 
Water, 45.32. Required the simplest symbol possible. 

Ans. Estimating the number of molecules of water (II»0), as 
if water were a fourth element with an atomic weight of 18, we get 
FeSO,. 1H,0. 

11. The percentage composition of morphia according to Liebig's 
analysis is Carbon, 71.35; Hydrogen, 6.69; Nitrogen, 4.99 ; Oxy- 
gen (by loss), 16.97. What is the symbol of this alkaloid, and how 
closely does this symbol agree with the results of analysis ? 

Ans. The symbol C l .Ji^N0 3 would require 71.58 Carbon, 6.66 
Hydrogen, 4.91 Nitrogen, and 16.85 Oxygen. 

12. It is required to find the weight of phosphorus in 155 kilos, 
of calcic phosphate (Ca 3 P 2 O g ). Ans. 31 kilos. 

13. It is required to find the weight of sulphuric anhydride (SO. d ) 
in 284 kilos, of sodic sulphate, Na.SO^ Ans. 160 kilos. 

14. How many grammes of plumbic sulphate (PbSOJ can be 
made from 2.667 grammes of sulphuric anhydride (S0 3 ) 

Ans. 10.1 grammes. 

15. How many grammes crystallized cupric sulphate (CaSO^ 
627 2 0) will yield 317 grammes of copper ? Ans. 1337 grammes. 

16. Required the total molecular weight of crystallized sodic 
phosphate, knowing that 71.6 parts of the salt contain 9.2 parts of 
sodium, and that the total atomic weight of sodium in one mole- 
cule of the compound is 46. Ans. 358. 



. : 



52 STOCHIOMETRY. 

17. The molecular weight of potassic nitrate is 101.1, and 2.359 
grammes of the salt ontain 1.120 grammes of oxygen. What is 
the total atomic weight of oxygen, and also the number of oxygen 
atoms in one molecule ? 

Ans. Total atomic weight 48. No. of oxygen atoms 3. 

18. How much nitric acid (HN0 3 ) is required to dissolve 3.804 
grammes of copper (Cw) and how much cupric nitrate (CwiV^Og) 
and how much nitric oxide (NO) will be fori»«d in the, process? 
The reaction is expressed by the equation 

ZCu + (8Bir0 8 +Aq) = (3CuN 2 6 +4B a O+Aq) + 2^®. 

Ans. 10.08 grammes of nitric acid; 11.244 grammes of cupric 
nitrate and 1.20 grammes of nitric oxide. 

19. How much common salt (NaCl) must be added to a solution 
containing 30 grammes of argentic nitrate (AgN0 3 ) in order to 
throw down the whole of the silver, and how much argentic chloride 
(AgCl) will be thus precipitated ? 

(AgN0 3 + JVaCl+Ag) = AgCl + {NaNO % + Aq). 

Ans. 10.32 grammes of salt and 25.32 grammes argentic chloride. 

20. How many litres of ammonia gas (J^TJ^t 3 ) and how many of 
chlorine gas @l-(oJl are required to make one litre of nitrogen gas 
S5T E IESr ? How many litres of hydrochloric acid gas (31 (fill) are 
also formed ? 

2ssnn 3 + 3®i-@i = 653(91 + ssm 

Ans. 2 litres of ammonia gas ; 3 litres of chlorine gas, and 8 
litres of hydrochloric acid gas. 

21. How many litres of hydrochloric acid gas (IHOl) and how 
many of oxygen gas ((£>(£)) can be obtained from one litre of 
aqueous vapor (HJ 2 @), and how many litres of chlorine gas 
((BJl-Ol) must be used in the process ? 

25H 2 (c) + 2@K91 = 4SJ@1 + (eXD. 

Ans. 2 litres of hydrochloric acid gas, £ litre of oxygen gas, and 
1 litre of chlorine gas. 

22. How many litres of oxygen gas (©<£)) are required to burn 
completely (i. e. to combine with) one litre of alcohol vapor 
(®2lS 6 '©), and how many litres of carbonic anhydride (0@ 2 ) and 
how many of aqueous vapor (m 2 @) are formed by the process ? 
The chemical reaction which takes place when alcohol burns is 
expressed by the equation 



STOCHIOMETRY. 53 

@ 2 IU 6 CD + 3®--® rz= 2(S© 2 + 3HT,®. 

Ans. 3 litres of oxygen gas ; 2 litres of carbonic anhydride, and 
3 litres of aqueous vapor. 

23. How many litres of oxygen gas are required to burn one 
litre of arseniuretted hydrogen (m 3 ^.s), and how many litres of 
arsenious acid vapor (^s® 3 ) and how many of aqueous vapor are 
formed in the process ? 

4^s + 9®=® = 4^.s® 3 + em,®. 

Ans. 2\ litres of oxygen gas ; 1 litre arsenious acid vapor and l£ 
litres of aqueous vapor. 

24. How many litres of chlorine gas can be made with 19.49 
grammes of manganic oxide (MnO-z) ? 

MnO*+(4HCl+Aq)==(MnCl 2 + 2JI i O + Aq)+®l-<&l 

Ans. 5 litres. 

25. How many grammes of chalk (CaC0 3 ) are required to yield 
one litre of carbonic anhydride ? 

CaC© 3 + (2BCI + Aq) = ( Ca Cl 2 + IT 2 0+Aq) + ®® 2 . 

Ans. 4.48 grammes. 

2G. How many litres of hydrochloric acid gas (HCl) can be made 
with 8.177 kilogrammes of common salt (NaCl) ? 

(2Na ci + mso 4 + Aq) = (M 2 so 4 +A q ) + 2 mm. 

Ans. 3120. 
27. How many grammes of ferrous sulphide (FeS) are required 



to yield 568 c. in. of sulphuretted hydrogen (T1. 2 S) 



FcS + {H 2 SO, + Aq) = (FeSOi + Aq) + Wfl. 

Ans. 2.24 grammes. 



CHAPTER VII. 

CHEMICAL EQUIVALENCY. 

26. Chemical Equivalents. — If in a solution of argentic 
sulphate we place a strip of metallic copper, we find after a 
short time that all the silver has separated from the solution, 
and that a certain quantity of copper has dissolved in its place. 

(Ag 2 S0 4 + Aq) + Cu = ( OuSOt + Aq) + Ag 2 . [25] 

If now we pour off the solution of cupric sulphate, and place 
in this solution a strip of metallic zinc, the metallic copper in 
its turn will all separate, and to replace it a certain amount of 
zinc will dissolve. • 

(CuS0 4 + Aq) + Zn=(ZnSOt + Aq) + Cu. [26] 

Lastly, if we pour off the solution of zincic sulphate, and 
place in this a strip of metallic magnesium, the zinc will in like 
manner be replaced by magnesium. 

(ZnSOt + Aq) + MS = (MgSO A + ■ Aq) + Zn. [27] 

In experiments like these, we can by proper analytical 
methods determine the relative quantities by weight of the 
several metals which thus replace each other, and we find that 
they are always the same. Thus, if our first solution contained 
108 milligrammes of silver, the amount of each metal suc- 
cessively dissolved and precipitated would be, of copper, 
31.7 m. g., of zinc, 32.6 m. g., of magnesium, 12 m. g. More- 
over, if, instead of using in our experiments a metallic sulphate, 
we take a metallic chloride, nitrate, acetate, or any other com- 
pound of the metals, we find that the same definite ratios are 
preserved, at least in every case where the substitution is pos- 
sible. It would appear then that these relative quantities of 
the several metals exactly replace each other in all such cases. 
They are, therefore, regarded as the chemical equivalents of 



CHEMICAL EQUIVALENCY. 55 

each other, in the sense that they are capable of filling each 
other's place. 

In a strict sense, two quantities of different elements can 
be said to be equivalent to each other only when they are 
actually capable of replacing each other in some known chem- 
ical reaction, but formerly the word was used with a much 
wider significance, and quantities of two different elements 
were said to be equivalent to each other if they had been 
proved to be equivalent to the same quantity of some third 
element which served as a link of connection. In this way 
an equivalency may be established between all the chemical 
elements, and the system of chemistry still used in many text- 
books is based on a system of equivalency so determined. If 
the table of chemical equivalents on this old system is com- 
pared with a table of atomic weights on the new, it will be 
found that the numbers of the one are either the same as those 
of the other, or el-e some very simple multiples of them. The 
one set of numbers can be used in all stochiometrical calcula- 
tions in the same way as the other, and on the old system the 
symbols stand for equivalent-, as in the new they stand for 
atomic weights. The equivalents have this advantage, that 
they are the result of direct experiments, and are based on no 
hypothesis in reirard to the molecular constitution of matter. 
But this hypothesis is necessary, in order to correlate a large 
number of facts which modern chemical investigation has 
brought to light, and when once made, the rest of the system 
follows as a necessary consequence. 

27. Quanti vale nee and Atomicity of the Elements. — If now, 
starting with the atomic weights as they have been determined 
or assumed in Table II., we compare together the different 
elements from the point of view taken in the last section, it 
will be found, that, while in some cases one atom of one ele- 
ment is the equivalent of one atom of another, in other cases, 
it may be the equivalent of two, three, or four atoms. Since 
in the system of this book the symbols always stand for atomic 
weights, the relation here referred to is made evident whenever 
any metathetical reaction is expressed in the form of an equa- 
tion. A few examples will illustrate the point, and make 
clear what is meant. The reaction of aqueous hydrochloric 
acid on a solution of argentic nitrate is expressed by the 
equation, 



56 CHEMICAL EQUIVALENCY. 



(AgN0 3 + HCl + Aq) = (HN0 3 + Aq) + AgCl, [28] 

and here evidently Ag changes places with H, and hence one 
atom of silver is equivalent to one atom of hydrogen. Take 
now the reaction of dilute sulphuric acid on zinc, which is 
expressed by the equation, 

Zn + {H 2 SO, + Aq) = (ZnSOi + Aq) + 53-33, [29] 

and it will be seen that Zn has changed places with H 2 , and 
hence that one atom of zinc is the equivalent of two atoms of 
hydrogen. Lastly, in the reaction of water on phosphorous 
trichloride, expressed by the equation, 

in 
H 3 H 3 3 + P Cl 3 = ZHCl + H 3 P0 3 , [30] 

Phosphorous Acid. 

it is equally evident that P has changed places with JT 3 , and 
hence in this reaction one atom of phosphorus is equiva- 
lent to three atoms of hydrogen. 

This relation of the elements to each other is called by 
Hofmann quantivalence ; and selecting here, as in the system of 
atomic weights, the hydrogen atom as our standard of reference, 
the atoms of different elements are called «<m*valent, fo'valent, 
trivalent, or quadrivalent, according as they are in the sense 
already indicated equivalent to one, two, three, or four atoms 
of hydrogen. These terms are very appropriate, since they 
are all derived from the same root as our common English 
word equivalent, which best expresses the fundamental idea 
that underlies the whole subject. We shall therefore adopt 
them in this book, and, as Hofmann recommends, designate 
the quantivalence, whenever important, by a Roman numeral 
placed over the atomic symbol thus, 

1 11 m iv 

ci, o, jsr, a 

In most cases, however, the quantivalence is indicated with 
sufficient clearness by the dashes, which are also used in this 
book to separate the parts of a molecular symbol. The num- 
ber of these dashes is always the same as the quantivalence 
of the atoms, or groups of atoms, on either side. 



CHEMICAL EQUIVALENCY. 57 

With these additions to our notation we are able to express 
by our symbols all that was valuable in the old system of 
equivalents, and at the same time all that is peculiar to our 
modern theories. 

Precisely the same relations of quantivalence are manifested 
even more fully by the compound radicals, whenever in a 
chemical reaction they change places with elementary atoms, 
and their replacing value is indicated in the same way. Thus, 
in the following reaction, 

CM s 6-Cl+H-0-ff=H-Cl'+H-0-C 2 H,d, [31] 

Acetyl chloride. Water. Acetic Acid. 

the radical C 2 H 3 0, named acetyl, changes places with one atom 
of hydrogen, and is therefore univalent, while in the next, 

in in 

cm ci 3 + HoJsr= sua + ch=-n, [32] 

Chloroform. Hydrocyanic Acid. 

the radical CH\s as evidently trivalent. 

The quantivalence of an element or radical is shown, not only 
by its power of replacing hydrogen atoms, but also by its power 
of replacing any other atoms whose quantivalence is known. 
Moreover, what' is still more important, the quantivalence of an 
element or radical is shown, not only by its replacing power, but 
also by what we may term its atom-fixing power, that is, by its 
power of holding together other elements or radicals in a mole- 
cule. We may take as examples the molecules of four very 
characteristic compounds, namely, hydrochloric acid, water, 
ammonia, and marsh gas, whose symbols may be written thus, 

I II III iv 

H-Cl K H-0 H, H, H=-N H, K #, HW. 

Hydrochloric Acid. Water. Ammonia. Marsh Gas. 

By these symbols it appears, that, while the univalent atom of 
chlorine can hold but one atom of hydrogen, the bivalent atom 
of oxygen holds two, the trivalent atom of nitrogen three, and 
the quadrivalent atom of carbon four atoms of the same ele- 
ment. It appears, then, that the Roman numerals or dashes, 
which represent the replacing power of the atoms or radicals, 
represent also the atom-fixing 'power of the same, measured 
in each case by the number of atoms of hydrogen, or their 



53 CHEMICAL EQUIVALENCY. 

equivalents, with which these atoms ar radicals can combine 
to form a single molecule. On account of the importance of 
this principle we will extend our illustrations to a number of 
other compounds, and the student should carefully compare 
in each case the quantivalence on the two sides of the dash 
or dashes, which mark the atom-fixing power of the dominant 
atom in the molecule. 

ii ii ii ii 

Na-Gl K-I C 2 ff 5 -Br K-CJST; 

Sodic Chloride. Potassic Iodide. Ethylic Bromide. Potassic Cyanide. 

i ii i ii n i ii i i n i 

K-O-H Pb-0 H-0-N0 2 HO-C 2 H,Oi 

Potassic Hydrate. Plumbic Oxide. Nitric Acid. Acetic Acid. 

i i i in i mil i in 

H, H, CJIfN ( C 2 H 5 )fP CH„ C 2 H r> , C 5 H^M 

Ethylamine. Triethyl phosphine. Methyl-ethyl-am>l-amine. 

The quantivalence of the chemical elements, especially as 
indicated by their atom-fixing power, is by no means always 
the same. They constantly exhibit under different conditions 
an unequal atom-fixing power. Thus we have 

ii iv in v m v 

Sn Cl 2 and Sn Cl» P Cl 3 and PCI 5 , NH Z and NH, CI. 

Each element, however, has a maximum power, which it never 
exceeds. This we shall call its atomicity, and we shall distin- 
guish the elements as monads, dyads, triads &c, according to 
the number of univalent atoms or radicals they are able at 
most to bind together. Thus nitrogen is a pentad, although 
it is more commonly trivalent, and lead is a tetrad, although 
it is usually bivalent. Again, sulphur is a hexad, alfhough 
in most of its relations it is, like lead, bivalent. In like 
manner with other elements, one of the few possible con- 
ditions is generally much more common and stable than the 
rest, and this prevailing quantivalence of an element is a 
more characteristic property than its maximum quantiva- 
lence or atomicity. A classification of the elements based on 
their atomicity alone would contravene their most striking 
analogies, while one based on the prevailing quantivalence 
very nearly satisfies all natural affinities. Moreover, it should 
be added, that, while the prevailing quantivalence of the ele- 
ments is generally well established, their atomicity is frequently 



CHEMICAL EQUIVALENCY. 59 

still in doubt ; for the first can generally be discovered by study- 
ing the simple compounds of the elements with chlorine or hy- 
drogen, while the last is often only manifested in those more 
complex combinations, in regard to which a difference of opin- 
ion is possible. 

The possible degrees of quantivalence of an elementary 
atom are related to each other by a very simple law. They 
are either all even or all odd. Thus the atom of sulphur may 
be sextivalent, quadrivalent and bivalent, but is never triva- 
lent or univalent ; and on the other hand the atom of nitrogen 
may be quinquivalent, trivalent and univalent, but not quad- 
rivalent or bivalent. Atoms like those of sulphur, whose quan- 
tivalence is always even, are called artiads, while those like 
nitrogen, whose quantivalence is always odd, are called 
perissads. 

A change in the quantivalence of an atom implies a change 
in all its chemical relations, and the differences between the 
reactions of the same atom in its several states of quantivalence 
are frequently as great as those between the atoms of different 
elements. Indeed, the first distinction appears to be only less 
fundamental than the last, to which chemists have attached so 
great and perhaps undue importance. The ferrous and ferric 
compounds of iron, for example, would be referred to different 
elements, were it not for the single circumstance that they may 
be derived from the same substance and are so readily converti- 
ble into each other. The classes of compounds to which they 
are most closely related belong indeed to wholly different ele- 
ments ; for the ferrous compounds resemble those of zinc, and 
the ferric compounds those of aluminum. A multitude of simi- 
lar facts will be brought to notice in Part II. of this work. 

28. Atomicity or Quantivalence of Radicals. — When in the 
molecule of any compound the dominant or central atom is 
united to as many other atoms as it can hold of that kind, the 
molecule is said to be saturated ; thus 

HCl, H.,0, H Z N, lf 4 

are all saturated molecules ; for, although nitrogen is a pentad, 
it cannot without the intervention of some other atom or radical 
hold more than three atoms of hydrogen. While on the other 
hand the molecules 

CO, PCl 3 and SnCl 2 






CO CHEMICAL EQUIVALENCY. 

are not saturated, for they can combine directly with more 
oxygen or chlorine, forming thus the saturated molecules 

00 2 , PCl 5 sndSnCl,. 

If now from a saturated molecule we withdraw one or more 
atoms of hydrogen, or their equivalents, the residue may be re- 
garded as a compound radical with an atomicity equal to the 
number of hydrogen atoms, or their equivalents, withdrawn. 
Thus, if from the saturated molecule of marsh gasi^Cwe 
withdraw one atom of hydrogen, we get the radical methyl 
B^C, which is a monad; if we withdraw two atoms, we have 
the radical, H>C, which is a dyad; if we withdraw three, 
there results TIG, which is a triad ; and lastty, if we with- 
draw all four, we fall back on the tetrad atom of carbon. Again, 
if from the saturated molecule of nitric anhydride N 2 & we 
withdraw one atom of the dyad oxygen 0, it falls into two 
atoms of NO. z each of which is a monad. If now we with- 
draw from NO.> one of its remaining atoms of oxygen, we 
have left NO, which is a triad. Lastly, a molecule of sulphuric 
anhydride SO s , which is saturated, gives, by withdrawing one 
atom of oxygen, S0. 2 , which acts as a bivalent radical. These 
considerations lead us to a simple rule, first stated by Wurtz, 
which in almost every case will enable us to infer the atomicity 
of any given radical. The atomicity 1 of a compound radical 
is always equal to the number of hydrogen atoms, or their equiva- 
lents, which the radical may be regarded as having lost. 

It must not be supposed, however, that all such radicals are 
possible compounds. In a few cases only these residues, of 
which we have been speaking, form non-saturated molecules, 
which are capable of existing in a free state, like those of car- 
bonic oxide, nitric oxide and sulphurous acid. At other times 
they are compound radicals, which, by doubling, form molecules 
that can exist in a free state, as those of cyanogen gas, and 
perhaps also of some hydrocarbons. Again, they appear as 
compound radicals, which pass and repass in so many chemical 
reactions as to almost force upon us the belief that they have 
a real existence, and represent the actual grouping of the 
atoms in the compounds of which they seem to be an in- 
tegral part. Still again, and even more frequently, they can' 
only be regarded as convenient factors in a chemical equation. 

1 The quantivalence of a compound radical is always the same as its 
atomicity. 



CHEMICAL EQUIVALENCY. 61 



Questions and Problems. 

1. Analyze the following metathetical reactions, showing in each 
case how many parts of the several elements are equivalent to one 
part by weight of hydrogen, and also to how many atoms of hydro- 
gen one atom of each of the interchanging elements corresponds. 
For the atomic weights refer to Table II. 

2H-0-O 2 H 5 + K-K= 2K-0-CH, + H-H 

Alcohol. Potassium. Potassic Ethylate. 

2H-OH + My =z Mg--0.fH 2 + HH 

"Water. Magnesic Hydrate. 

Sb-=Offf 8 + SHCl = SO CI, + 3HOH. 

Antimonious Hydrate. AniimOnious Chloride. 

4H-0-H+ SiOt 4 = H£OfSi + UiOl 

Silicic Chloride. Silicic Acid. 

2 Make out a table of chemical equivalents so far as the reactions 
of this chapter will enable you to deduce them from the atomic 
weights given in Table II. 

3. Analyze the following metathetical reactions, showing in each 
case how the quantivalence of the several compound radicals in- 
volved in the metathesis, is indicated. 

H-0-H+ (0,11,0)- 0-(a z H-)=(C 2 H,0)-0-H-\-H-0-{a 2 H 5 ). 

Water. Acetic Ether. Acetic Acid. Alcohol. 

2K-{CN) + (0,H 4 )-Br 2 = (0 2 H 4 )-(ON) 2 + 2KBr. 

Potassic Cyanide. Ethylene Bromide. Ethylene Cyanide. Potassic Bromide. 

3II-0-H + (O.H^OI, = (OsH^-OfH 3 + 3 HOI. 

Water. Glyceryl Chloride. Glycerine. Hydrochloric Acid. 

The names of the radicals are as follows : CJIfi, Acetyl ; C 2 H 51 
Ethyl ; C 2 // 4 , Ethylene ; C z H b , Glyceryl ; CN, Cyanogen. 

4. "What is the atom-fixing power or quantivalence of the differ- 
ent atoms and radicals in the following symbols ? 

KfSfSbS . HNa - Of 00 (NH 4 )- -NO 

Potassic Sulphantimonite. A id Sodic Carbonate. Amnionic Ni rite. 

BfNfC 2 2 (HO)<(H 2 N)=( 4 H 4 2 ) K,Sb=0 4 W 4 H,0 2 . 

Oxamide. Succinamic Acid. Tartar Emetic (dried). 

5. If Hfi ; C 2 # 6 ; C 2 Hfi (alcohol) ; COC! 2 (phosgene gas) ; 
C 2 Hfi 2 (acetic acid) and C 2 H 2 4 (oxalic acid) are saturated mole- 
cules, what is the atomicity of the radicals 110 (hydroxyl) ; CH S 
(ethyl); CJI 4 (ethylene); CJM) (aldehyde); CO (carbonyl) ; 
CJI.fi (acetyl) and Cfi. 2 (oxalyl). 



CHAPTER VIII. 

CHEMICAL TYPES. 

29. Types of Chemical Compounds. — There are three 
modes or forms of atomic grouping, to which so large a num- 
ber of substances may be referred, that they are regarded as 
molecular types, or patterns, according to which the atoms of 
a molecule are grouped together. These types may be repre- 
sented by the general formulas : — 

T TT T 

[33] 



ii i i n 
R-R R, R=R 


i n i 
or R-R-R 


i i i in 
R, R, R=-R or 


i i m i 
R, R-R-R. 



It will be noticed, that in the first of these types a single uni- 
valent atom or radical * is united to another single univalent 
atom, that in the second a bivalent atom binds together two 
univalent atoms or their equivalents, and that in the third a 
trivalent atom binds together three univalent atoms, or their 
equivalents. The dashes are used to separate what has been 
called the central, the dominant, or the typical atom from those 
which it thus unites into one molecular whole, and serve at 
the same time to point out the parts of the symbol to which 
its affinities are directed. Commas are used to separate the 
subordinate atoms so united. It will be further noticed, that 
in each case the quantivalence of the dominant atom is equal 
to the sum of the quantivalences of the subordinate atoms, or 
radicals, on either side; and the peculiarity in each case consists 
solely in the relations of the parts of the molecule which we 
thus attempt to indicate by the symbol. The three compounds, 
hydrochloric acid, water, and ammonia, 

ii ii n iiini 
H-Cly H,H=0, H y H,H*N, 

1 Here, as elsewhere through the hook, we use the symbol R for any 
n in 

univalent, R for any bivalent, and R for any trivalent atom or radical. More- 
over, to avoid unnecessary repetition, we shall for the future conform to the 
general usage, and speak of the atoms of a radical as well as of those of an 
element, and use the word " atom " as applying to both, although the usage 
frequentlv involves an obvious solecism. 



CHEMICAL TYPES. 63 

are generally taken as representatives of these types, and sub- 
stances are described as belonging to the type of hydrochlo- 
ric acid, to the type of water, or to the type of ammonia, as 
the case may be. These substances, however, are regarded as 
types in no other sense than that their molecules present the 
same mode of grouping which is indicated above by the more 
general symbols. Substances belonging to the same type may 
have widely different properties. To the type of water be- 
long the strongest alkalies and the most corrosive acids known. 
In what, then, it may be asked, does the type outwardly con- 
sist, or in what is it manifested? for the grouping of the atoms 
can only be a matter of inference. The answer is, that the 
type of the molecules of a substance is manifested solely by 
its chemical reactions. Substances belonging to the same type 
are simply ihose whose reactions may be classed together ac- 
cording to some one general plan. Thus water, alcohol, and 
acetic acid are classed in the same type, because, when submit- 
ted to the action of the same or similar reagents, they undergo 
a like transformation, which seems to point to a similarity of 
atomic grouping. 

H HO + PCI, = PCI,0 + H-Cl + H-Cl 

Water. Phosphoric Chloride. Hydrochloric Acid. 

^ C,H,0 + PCl 6 = PChO + H-Cl + C,H 5 -Cl [34] 

Alcohol. Phosphoric Oxy-chloride. Ethylic Chloride. 

H, C,H,0-0 + PCI, = PC1 3 + H-Cl + CH^O-Cl 

Acetic Acid. Acetylic Chloride. 

On studying these reactions, it will be seen that both the man- 
ner in which the three compounds break up, and the probable 
constitution of the products formed, point to the conclusion, that, 
in each, one bivalent atom holds together two univalent atoms 
or radicals. It will be found, in the first place, that in all three 
cases the reaction consists primarily in the substitution of two 
atoms of chlorine for one of oxygen in the original molecule. 
It will appear, in the next place, that as soon as this dominant 
atom, which holds together the parts of the molecule, is taken 
away, each of the three molecules splits up into two others of a 
similar type ; and lastly, it is evident from the third example 
that one of the oxygen atoms of acetic acid stands in a very 
different relation to the molecule from the other. All this 



64 CHEMICAL TYPES. 

points to the inference just made. At least, these and a vast 
number of similar reactions are best explained on this, hypoth- 
esis, and herein its only value lies and its probability rests. 
In section 27 we have already given the symbols of a number 
of chemical compounds so printed that they can be at once re- 
ferred to one or the other of the three types here alluded to, 
and it will not, therefore, be necessary to multiply examples in 
this place. 

30. Condensed Types. — In the same way that a bivalent 
atom may bind together two univalent -atoms or their equiva- 
lents, so, also, it may serve to bind together two molecules, and, 
in like "manner, a trivalent atom may bind together three mole- 
cules into a more complex molecular group ; and thus are 

formed what are called condensed types. We may represent 
*) i ii i 

a double molecule of the type of water thus, R 2 =R 2 =R 2 , but 
it must be borne in mind that such a symbol stands for two 
molecules, since, by the very definition, two molecules of the 
same kind cannot chemically combine. We can, however, 

solder them, as it were, into one molecular whole by substituting 

i ii 

for the two univalent atoms R 2 a single bivalent atom R, 

when we obtain a mode of molecular grouping represented by 

i ii n 
R 2 =R.rR, [35] 

which may be called the type of water doubly condensed. The 
constitution of common sulphuric acid is best represented after 
this type by the symbol, — 

B 2 -0 2 =S0 2 . [36] 

n 
The soldering atom is here the bivalent radical S0 2 . In like 

manner, by using a trivalent atom, we can solder together 

three molecules of the same water-type, as in the general 

symbol, — 



i n m 
Rg-R 3 =R, 



[37] 



which represents the type of water trebly condensed. In the 
same way we may derive the symbol, — 



-£vQj x£q""*^*2 -*-hy 



[38] 



CHEMICAL TYPES. 65 

which represents the type of ammonia doubly condensed. The 
substance urea, one of the most important of the animal secre- 
tions, is best represented by a symbol after this last type, — 

m ii 
H 2 , HjtNfCO [39] 

where the soldering atom is the bivalent radical carbonyl. 

Chemists have also been led to admit the existence of what 
are called mixed types, which are formed by the union of mole- 
cules of different types soldered together by a single multiva- 
lent atom or radical as before. Thus, the molecules of sul- 
phurous acid may be regarded as formed of a molecule of water 

soldered to a molecule of hydrogen by an atom of sulphuryl, 
ii ii 

S0 2 ; thus, H-O-H and H~H, united by S0 2 give 

H-0-S0 2 -H. C 40 J 

So, also, the composition of a complex organic compound 
called sulphamide, or sulphamic acid, is most simply expressed 
when regarded as formed by the union of water and ammonia 
soldered together by the same radical sulphuryl ; thus, from 

in n in n ii 

H, H-N-H, and H-O-H we have H, H=NS0 2 -0-H [41] 

Lastly, if we bind together on the same principle molecules 
of the type of hydrochloric acid, we shall simply reproduce 
the types of water and of ammonia, thus showing that all the 
types are only condensed forms of the simplest. We must not, 
therefore, attach to the idea of a chemical type any deeper sig- 
nificance than that indicated above. It is simply a conven- 
ient mode of classifying certain groups of chemical reactions, 
and a help in representing them to the mind ; and we may 
regard the same substance as formed on one type or on the 
other, as will best help us to explain the reactions we are study- 
ing. Moreover, it is frequently convenient to assume other types 
besides those here specially mentioned. 

31. Substitution. — When cotton-wool is dipped in strong 
nitric acid (rendered still more active by being mixed with 
twice its volume of concentrated sulphuric acid), and after- 
wards washed and dried, it is rendered highly explosiye, and, 
5 






66 CHEMICAL TYPES. 

although no important change has taken place in its outward 
aspect, it is found on analysis to have lost a certain amount of 
hydrogen and to have gained from the nitric acid an equivalent 
amount of nitric peroxide N0 2 in its place. 

C 6 (H w )0 5 becomes C 6 (ff 7 (N0 2 ) 3 )0 5 . 

Cotton. Gun-Cotton. 

Under the same conditions glycerine undergoes a like change, 
and is converted into the explosive nitro-glycerine, — 

C 3 (lf 8 )0 3 becomes C 3 (R 5 (JST0 2 ) 3 )0 3 . 

Glycerine. Nitro-glycerine. 

So, also, the hydrocarbon naphtha, called benzole, is changed 
into nitro-benzole, — 

C 6 B G becomes <7 G (# 5 ,2V0 2 ). 

Benzole. Nitro-benzole. 

The last compound is not explosive, and the explosive nature 
of the first two is in a measure an accidental quality, and is 
evidently owing to the fact that into an already complex struc- 
ture there have been introduced, in place of the indivisible atoms 
of hydrogen, the atoms of a highly unstable radical rich in oxy- 
gen. The point of chief interest for our chemical theory is that 
this substitution does not alter, at least essentially, the outward 
aspect of the original compound. Every one knows how closely 
gun-cotton resembles cotton-wool. In like manner nitro-glycer- 
ine is an oily liquid like glycerine, and nitro-benzole, although 
darker in color, is a highly aromatic volatile fluid like benzole 
itself. Products like these are called substitution products, and 
they certainly suggest the idea that each chemical compound 
has a certain definite structure, which may be preserved even 
when the materials of which it is built are in part at least 
changed. If in the place of firm iron girders we insert weak 
wooden beams, a building, while retaining all its outward as- 
pects, may be rendered wholly insecure, and so the explosive 
nature of the products we have been considering is not at all 
incompatible with a close resemblance, in outward aspects and 
internal structure, to the compounds from which they were 
derived. 

The idea that each body has a definite atomic structure is 



CHEMICAL TYPES. 67 

even more forcibly suggested by another class of substitution 
products first studied by Dumas, in which atoms of chlorine, 
bromine, or iodine have taken the place of the hydrogen atoms 
of the original compound. Thus, if we act upon acetic acid 
with chlorine gas, we may obtain three successive products, as 
shown in the following table, although only the first and the 
last have been fully investigated. 

Acetic acid C 2 i7 4 <9 2 or (C 2 H 3 6)-0-H 

Chloracetic acid C 2 (H 3 CI)0 2 " (C 2 H 2 ClO)-0 -H 

Dichloracetic acid C 2 (H 2 C1 2 )0 2 « (C 2 HCl 2 6)-0-lf 

Trichloracetic acid C 2 (HC1 3 )0 2 " (C 2 Cl z b)-0-H 

We cannot, however, replace the fourth atom of hydrogen 
by chlorine ; and this fact seems to prove that there is a real 
difference between this atom of hydrogen and the other three, 
and gives an additional ground for the distinction we make 
when we write the symbol of acetic acid after the type of water, 
as in the second column. The three atoms of hydrogen in the 
radical placed on the left-hand side of the dominant atom may 
all be replaced by chlorine, but the single atom of hydrogen 
placed on the right cannot. These products all resemble 
acetic acid in that they form with the alkalies crystalline 
salts, when the fourth atom of hydrogen is replaced by an 
atom of sodium or potassium, as the case may be. 

It was the study of these and similar substitution products 
which first led to the conception of chemical types, and the 
word as first used was intended to convey the idea of a definite 
structure, although perhaps as yet unknown ; but as the theory 
was extended more and more, and to widely different chemical 
compounds, it was found that the first definite conception could 
not be maintained, and the idea gradually assumed the shape we 
have given it in the last section. Still, the facts from which 
the original conception was drawn remain, and they point no 
less clearly now than they did before to the existence of a def- 
inite structure in all chemical compounds as the legitimate ob- 
ject of chemical investigation. 




68 CHEMICAL TYPES. 

32. Isomorphism. — Closely associated with the facts of the 
last section, which find their chief manifestation in substances 
of organic origin, are the phenomena of isomorphism, which 
are equally conspicuous among artificial salts and native min- 
Fi g . i. erals. There seems to be an intimate 

connection between chemical composition 
and crystalline form, and two substances 
which under a like form have an anal- 
ogous composition are said to be isomor- 
phous. Thus the following minerals all 
crystallize in rhombohedrons (Fig. 1,) 
which have very nearly the same inter- 
facial angles, and, as the symbols show, 
they have an analogous composition. They are therefore 

isomorphous. 

ii n n 
Calcite or calcic carbonate Ca=O^CO 

ii n ii 
Magnesite or magnesic carbonate Mg=0,=CO 

ii ii ii 
Chalybdite or ferrous " Fe=0 9 =CO 

ii ii ii 
Diallogite or manganous " Mn=O^CO 

ii ii ii 
Smithsonite or zincic " Zn=0.=CO 

The most cursory examination of these symbols will show 
that they differ from each other only in the fact that one me- 
tallic atom has been replaced by another. It is not, however, 
every metallic atom which can thus be put in without altering 
the form. This is a peculiarity that is confined to certain 
groups of elements, which for this reason are called groups of 
isomorphous elements. Moreover, as a rule, there is a close re- 
semblance between the members of any one of these groups in 
all their other chemical relations. These facts, like those of the 
last section, tend to show that the molecules of every substance 
have a determinate structure, which admits of a limited substi- 
tution of parts without undergoing essential change, but which 
is either destroyed or takes a new shape when in place of one 
of its constituents we force in an unconformable element. A 
well-known class of artificial salts, called the alums, affords even 
a more striking illustration of the principles of isomorphism 
than the simpler example we have chosen ; but all the bearings 



CHEMICAL TYPES. 69 

of the subject cannot be understood without a knowledge of 
crystallography, and we must therefore refer for further details 
to works on mineralogy. /.- 

33. Rational Symbols. — Chemical formulae, like those of 
the last few sections, which endeavor, by grouping together the 
elementary symbols, to illustrate certain classes of reactions, 
and to illustrate the manner in which a complex molecule may 
break up, are called rational symbols, and are to be distinguished 
from the simpler symbols used earlier in the book, which ex- 
press only the relative proportions in which the elements are 
combined, and which, since they are simply expressions of the 
results of analysis on a concerted plan, are called empirical 
symbols. Whether these rational symbols can be regarded in 
any sense as indicating the actual grouping of the material 
atoms is very doubtful, although facts like those stated above 
would seem to indicate that such may be the case, at least to a 
limited extent. It is difficult, for example, to resist the con- 
clusion that in alcohol and its congeners the atoms C 2 H 6 are 
grouped together in some sense apart from the rest of the 
molecule; but then we have no evidence of this grouping apart 
from the reactions of these compounds, and, until greater cer- 
tainty is reached, it is not best to attach a significance to our 
symbols beyond the truths they are known to illustrate. 

It is objected to the use of rational symbols that they bias 
the judgment on the side of some theory, of which they are 
more or less the exponents. But when they are used in the 
sense stated above, this objection has no force, for the reactions 
they prefigure are no less facts than the definite proportions they 
conventionally represent, and we employ one mode of grouping 
the symbols or another, as will best indicate the reactions we 
are studying. Moreover, as science advances, we have every 
reason to believe that we shall gain more and more knowledge 
of the actual relations between the parts of a material molecule, 
and as has already been intimated, there can hardly be a 
doubt that in some cases our rational symbols do express even 
now actual knowledge of this sort, however crude and partial 
it may be. Our present typical symbols are indeed the ex- 
pressions of partial generalizations, which, however imperfect, 
have an element of truth. Hence it is that they have pointed 
out new lines of investigation, have led to new discoveries, and 



70 CHEMICAL " TYPES. 

have been of the greatest value to science. They will doubt- 
less soon be superseded by other rational symbols, expressing 
other partial generalizations, to serve the same purpose in their 
turn and be likewise forgotten. We must not, however, de- 
spise these temporary expedients of science. They are not only 
useful, but necessary, and cannot mislead the student if he re- 
members that all such aids are merely the scaffoldings around 
the science, on which the builders work. It is from this point 
of view alone that we are to look at the whole idea of chemi- 
cal atoms, which lies at the basis of our modern chemical 
philosophy. That this idea is actually realized in the concrete 
form which it takes in some minds, can hardly be believed. 
The true chemical idea of the atom is more nearly represented 
by the corresponding Latin word individuum. The atom is 
the chemical individual, the unit, in which the mind seeks to 
repose for the time the individuality of that as yet undivided 
substance we call an element. 

34. Graphic Symbols. — A more graphic method of repre- 
senting the relations between the atoms of a molecule than 
that of our ordinary rational symbols has been contrived by 
Kekule, and has a similar value in aiding the conceptions, and 
thus facilitating the study of chemistry. In describing this 
system we shall speak of the possibilities of combination of 
any polyad atom with monad atoms as so many centres of at- 
traction or points of attachment, and, also, as so many affinities. 
Kekule represents a monad atom, with its single centre, thus, 0, 
while the symbols (•""T) , (■ ■ -) , (• • • -\ &c, represent 
polyad atoms of different atomicities. When the several affini- 
ties are satisfied, the points are exchanged for lines pointing 

in the direction of the attached atoms. Thus, the symbol ^^<J 

represents a dyad atom with its two affinities satisfied by two 

n 
monad atoms, as, for example, in a molecule of water H-O-H. 

In like manner the symbol ^ ( y^X|^(|~p(r^ re pre- 

v II 

sents a molecule of nitric anhydride N t O^ and the symbol 
( i 11 l! a rao ^ ecu ^ e °f sulphuric anhydride S0 3 . Mole- 
cules like these, in which all the affinities are satisfied, are said to 



CHEMICAL TYPES. 71 

v 
be saturated or closed, while the atomic group N0 2 , represented 

by > — ^ '—^ has one point of attraction still open, and, 

therefore, acts as a monad radical. So, also, the molecular 
group S0 2 represented by > — " '' * , acts as a dyad radi- 
cal. 

These graphic symbols enable us to illustrate several impor- 
tant principles which could not readily be understood without 
their aid. 

First. In the examples given in this section thus far, the 
quantivalence of a group of atoms of the same element is 
equal to the sum of the quantivalences of all the atoms of the 

v II 

group. Thus, in the molecule JV 2 5 , the group of two pentad 
atoms presents ten affinities, and is saturated by the group of 
five dyad atoms, which presents the same number of affinities 
in return. So, also, in the molecule S0 3 , a group of three 
dyad atoms just saturates the single hexad atom S. Such, how- 
ever, is not necessarily the case, for it frequently happens that 
the similar atoms of such groups are united among them- 
selves, and that a portion of the affinities (necessarily always 
an even number) are thus satisfied. For example, although 
C is a tetrad atom, the hydrocarbons, C 2 H^ C 2 H Y and C.,H 2 , are 
all saturated molecules, as is shown by the following graphic 
symbols, 

C 2 H G C 2 H t C 2 H 2 

and it is evident that in the first the two carbon atoms have 
been united by two, in the second by four, and in the third by 
six, of their eight affinities, while a corresponding number of 
points to which hydrogen atoms might otherwise have been at- 
tached are thus closed. 

In like manner we have a well-known series of hydrocar- 
bons, whose symbols are 

G/z^, C 2 Hq, C 3 IT 8 , C 4 IT w , C 5 H V2 , C G ff w &c, 

the molecule of each one differing from that of the last by the 
group CH 2 . In all these compounds the carbon atoms are 



72 CHEMICAL TYPES. 

united among themselves at the smallest possible number of 
points, as is shown, in a single case, by the following graphic 
symbol, 

CvTTTiTrrrTj jrirnc ■ ■ o 

OXiX' fr J i 'X 'X' fr J J iX 'X'XO 

and by constructing the graphic symbols of the other members 
of the series, it will be easily seen that the number of affinities 
thus closed is in every case equal to 2 n — 2, while the number 
remaining open is An — (2 n — 2) = 2 n -\- 2, where n 
stands for the number of carbon atoms in the molecule. Hence, 
while the groups just mentioned form saturated molecules, the 
atomic groups 

CB, C 2 ff 5 C s ff 7 C,H, C^n&c, 

Methyl. Ethyl. Propyl. Butyl. Ainyl. 

act as univalent radicals. The graphic symbol of ethyl is 

rVhf iY'/i i ^' aD< ^ m a s ' m ^ ar wa y tne graphic symbols of 
the other radicals may be easily constructed. In like manner 
may be also constructed the graphic symbols of the following 
important compound radicals, which form a series parallel to 
the first, and are all evidently dyads : — 

CM, C 8 H 6 C 4 H 8 C 5 R 10 &c. 

Ethylene. Propylene. Butylene. Amylene. 

Here again the graphic symbols enable us to explain a remark- 
able fact. These last atomic groups act not only as compound 
radicals, but also form the molecules of definite hydrocarbons 
(the first in the series being the well-known olefiant gas), and 
the difference in these two conditions may be represented to 
the eye, in the case of amylene, for example, as below : — 



Radical C 5 H 10 . 

Hydrocarbon C r ,H 10 . 

The molecule in the first case is open, and presents two points 
of attraction, while in the second case it is closed. 




CHEMICAL TYPES. 73 

The members of the two classes of hydrocarbon radicals 
mentioned above are the characteristic constituents of an im- 
portant class of compounds called alcohols, and hence they are 
usually called alcohol radicals. If, in these atomic groups, we 
substitute oxygen for a portion of the hydrogen, one atom of 
oxygen always taking the place of two atoms of hydrogen, we 
obtain still other series *)f radicals, which are the characteristic 
constituents of several important organic acids, and belong to 
the class of acid radicals, which will be defined in the next 
chapter. Among the most important of the radicals thus de- 
rived are those of the following series : — 

CHO C\H ? ,0 C s R,0 C A H 7 C 5 H s O 

Fortnyl. Acetyl. Propionyl. Butyryl. Valeryl. 

and the student should construct the graphic symbol of each. 

The compounds of carbon have been selected to illustrate 
the apparent change of atomicity which frequently accompa- 
nies the grouping together of similar atoms, because this ele- 
ment is peculiarly susceptible of such a mode of combination, 
and in fact the almost infinite variety of its compounds may be 
traced to this circumstance. The same phenomenon, however, 
is presented, although to a less marked degree, by other ele- 
ments. Thus arises the remarkable fact that a group of two 
atoms of a bivalent element has not unfrequently only the same 
quantivalence as a single atom. For example, there are two 
compounds of mercury and chlorine Hg^Ch represented graphi- 
cally by ©5 and [£Ty.r\ = Cl 2 represented by O^- So also 

we have Cu = and [Cu.^\=0. We also frequently meet with 
another illustration of the same principle in an important class 
of tetrad elements whose atoms readily pair together, forming 
an atomic group which is sexivalent. Thus are formed the 
well-known compounds 

lAl^lCk lFe^W 8 [CV 2 ]I0 3 ,&c. 

When these same elements enter into combination by single 
atoms, they are almost invariably bivalent, and thus we have, 
in several cases, two very distinct classes of compounds, the 
one formed with the single and the other with the double atom 
of the element ; for example, 




CHEMICAL TYPES. 

Fe~-Cl 2 and [i^ 2 ]IC7 6 Fe-0 and [JfoJiOg. 

It will be noticed that although in the compounds of the 
second class the quantivalence of the single atoms is twice as 
great as it is in the first, yet their atom-fixing power is only 
increased by one half, and hence the name of sesqui-oxides 
or sesqui-ch\orides, &c, which is frequently applied to them. 

In order to distinguish the groups of similar atoms whose 
affinities are all open, from those groups where the affinities are 
in part closed by the union of the atoms among themselves, we 
may, as above, enclose the symbols of the last in brackets ; and 
this rule will generally be followed. In most cases, however, 
the relations of the parts of the symbol are sufficiently evident 
without this aid. 

Secondly. The graphic symbols illustrate another important 
theoretical principle, which, although almost self-evident, might 
be overlooked if not dwelt upon specially ; namely, that 
on the multivalence of one or more of its atoms depends the 
integrity of every complex molecule. According to our pres- 
ent theories, no molecule can exist as an integral unit unless its 
parts are all bound together by such atomic clamps. More- 
over, the whole virtue of a compound radical consists in the 
circumstance that it is an incomplete structure of the same sort, 
and its quantivalence is in every case equal to the number of 
univalent atoms (or their equivalents) which are required to 
complete it, or which it may be regarded as having lost. 
Hence the law of Wurtz finds a perfect expression in this sys- 
tem of graphic notation. 

Thirdly. The graphic symbols illustrate most forcibly the 
relations of the parts of a complex molecule. Thus, for ex- 
ample, the symbols of alcohol and acetic acid given below show 
q p) that in these compounds the dominant (T~T) 
(J) atom of oxygen acts as a bond uniting (TY7) 
a complex radical to a single monad 
atom. They also show how it is 
possible that three of the atoms of 
hydrogen in acetic acid may stand in 
a very different relation to the mole- 
cule from the fourth (31). Again 
they show that the molecule of acetic 







e 
© 
e 

Alcohol. 
C.U.-O-H. 




© 

e-j 



acid differs from that of alcohol in the 



Acetic Acid. 
C 9 HoO-0~H. 



CHEMICAL TYPES. 



75 



fact that one dyad atom has taken the place of two monad 
atoms ; and, lastly, they give form to the idea of chemical 
types, so far as it has any real significance. When the com- 
position of a compound is represented in this way, all the 
accidental or arbitrary divisions of our ordinary notation dis- 
appear, and only those are preserved which are fundamental. 
We gain thus more accurate conceptions of molecular struc- 
ture. We understand better the relations of the various com- 
pound radicals (compare § 28), and, above all, we thus realize 
the full meaning of the fundamental tenet of our new philoso- 
phy, which holds that each chemical molecule is a completed 
structure bound together in all its parts by a system of mutual 
attractions. 

There is another system of graphic symbols, frequently used 
in works on modern chemistry, which has some advantages 
over the one just described. In this system the atoms are 
represented by small circles circumscribing the ordinary sym- 
bol, and the atomicity is indicated by dashes radiating from 
these circles. A few examples will sufficiently illustrate the 
application of this method. 

® ® 

®-©-©-®-@ 
® 

Acetic Acid. 
C 2 H s O.O-H. 



® ® 
®-®-@ ©-©-©-©-© 



Water 
H-O-H 



® ® 

Alcohol. 
C,Hr-0-H. 



It is obvious, however, that the circles here used are not es- 
sential, and if we omit them, and only use dashes between the 
dominant atoms, and also, for convenience in printing, bring the 
whole expression into a linear form, using commas to separate 
disconnected atoms, and such other signs as may be necessary to 
avoid ambiguity, we have at once the ordinary system of nota- 
tion adopted in this book. The graphic symbols last described 
are merely an expansion of this system. Nevertheless, the prac- 
tice of developing the ordinary symbols into either of the more 
graphic forms will tend to impress the full meaning of the 
symbols on the mind of the student, and will thus greatly aid 
him in acquiring a clear conception of the theory of modern 
chemistry. 



76 CHEMICAL TYPES. 

We may, however, extend the use of dashes so as to indicate 
the relations of all the parts of a complex molecule by our or- 
dinary notation. Thus we may write the symbol of alcohol 

([C-C]iJI 5 )-0-ff, 
or that of acetic acid 

dc-c^ir 3 ,o)-o-ff, 

and these expanded symbols may frequently be used to ad- 
vantage in place of the graphic forms. When thus developed, 
the symbol indicates the quantivalence of each of the atoms of 
the molecule, and in every case, if the symbol is correctly 
written, the number of dashes will be one half of the total 
quantivalence of all the atoms which are thus grouped together, 
for each dash evidently represents two affinities. 

The remarks at the close of the last section apply, of course, 
still more forcibly to such bold and material conceptions as 
these graphic symbols appear to represent, and when we re- 
call the hooked atoms of an elder philosophy, we cannot but 
smile to think how closely our modern science has reproduced 
what we once considered as strange and grotesque fancies. But, 
absurd as such conceptions certainly would be, if we supposed 
them realized in the concrete forms which our diagrams em- 
body, yet, when regarded as aids to the attainment of general 
truths, which in their essence are still incomprehensible, even 
these crude and mechanical ideals have the very greatest value, 
and cannot well be dispensed with in the study of science. 



Questions and Problems. 

1. To what types may the following symbols be referred, and what 
is the quantivalence of the different compound radicals here distin- 
guished ? Study with the same view the symbols already given in 
the previous chapter. 

H-(C,H 5 ) H(C 7 H b O) C,H A Kf0 2 =(C 2 H 2 0) 

Benzole. Oil of Bitter Almonds. Ethylene. Gly collie Acid. 

ff-0-(C,H 5 ) H-0-(C 7 H,0) RfO^CM,) H 2 =Of(C 2 2 ) 

Phenic Acid. Benzoic Acid. Glycol. Oxalic Acid. 

H, H, ( G 6 ff 5 )-=JST H, K ( G 7 H 5 0)*N 

Aniline. Benzamide. 

R 2 , 74 (C 2 H A )W 2 R 2 , H 2 . (a0 2 )lN 2 

Ethylene diamine. Oxamide. 



CHEMICAL TYPES. 77 

H, H-N( C 2 H 2 0)0-H H, H-N-( C 2 2 )- 0-H 

Glycocol. Oxamic Acid. 

H, (C 7 H 5 0)-N-(C 2 H 2 0)-0-H H, H=N-(C 2 O,)-0-(C 2 H 5 ) 

Hippuric Acid. Oxamethane. 

2. Analyze the following reactions, and show that by comparing 
the reactions in each group, the typical structure of the various 
compounds may be inferred. 

CI- CI + HH = HCl -f HCl 

Chlorine gas. Hydrogen gas. Hydrochloric Acid. Hydrochloric Acid. 

Cl-Cl + (C 7 H,0)-H = (C 7 H 5 0)-CI + HCl 

Oil of Bitter Almonds. Benzoyl Chloride. 



H-Cl + ■ K-O-H = KCl + H-O-H 

Potassic Hydrate. Potassic Chloride. Water. 

H-Cl + (C 2 H 5 )-0-H = (C 2 H 5 )-Cl + H-O-H 

Alcohol. Ethylic Chloride. 



H,HS + PiCh = PWl 3 ,S + HCl + HCl 

Sulphohydric Acid. Phosphoric Chloride. 

H ( C 2 H, 0)-S + Pi Cl 5 = Pi Cl 3 , S + ( C,H, 0)- CI + HCl 

Thiacetic Acid. Acetyl Chloride. 

KrO.fH + (CO), H=-JST = KfOf(CO) + H, H &JST 

Potassic Hydrate. Cyanic Acid. Potassic Carbonate. Ammonia. 

K 2 =0.fH 2 +(CO).(C 2 H^=-]V=K 2 =0.r(CO)+KH(C,H 5 )=-B' 

Cyanic Ether. Ethylamine. 

3. What would be the symbols of cyanic acid and cyanic ether (see 
last problem), on the supposition that they contain the radical cyan- 
ogen, and are formed after the water type ? Is the following reaction 
compatible with that last given ? 

K-O-H + (C 2 H)-0-(CN) = (C 2 H)-0-H+ K-O-(CN)} 

Cyanetholine. Alcohol. Potassic Cyanate. 

and if not, what conclusion must you draw in regard to the two 
compounds cyanic ether and cyanetholine ? 

4. What bearing have the phenomena of substitution on the doc- 
trine of chemical types ? Does the circumstance that the proper- 

1 This product in the actual process is decomposed by the excess of potash 
into potassic carbonate and ammonia. 



78 CHEMICAL TYPES. 

ties of the substitution products are frequently quite different from 
those of the original substance invalidate the doctrine ? 

5. How does the action of chlorine on acetic acid indicate that 
this compound is fashioned after a determinate type ? On what 
particular fact does this evidence chiefly rest V 

6. What bearing have the phenomena of isomorphism on the doc- 
trine of types ? Enforce the argument by some familiar illustra- 
tion. 

7. The radical allyl C 3 H 5 is univalent in oil of garlic (C 8 H 6 \=S t 
and in allylic alcohol (C s H 5 )-0-H, but trivalent in glycerine 
(C 3 i7 5 )=0 3 =Z7 3 . Moreover, this radical when set free doubles, forming 
a volatile hydrocarbon oil, which has the composition (C 3 Z/ 5 )s(C 3 i9 5 ), 
and which combines directly with bromine, the resulting product hav- 
ing the symbol (C 3 i/ 5 )-(C 3 i7 5 )=i5r 4 . Represent these symbols by the 
graphic method, and thus explain the different relations of the 
radical. 

8. Represent the symbols of phenic acid and benzoic acid by the 
second graphic method, and explain why the radical phenyl (C 6 H b ) 
and benzoyl (C 7 // 5 0) are only univalent. 

9. Why is it that the addition of the atoms CH 2 does not change 
the atomicity of a radical ? 

10. W T hat is the quantivalence of Al in the symbol \_Al -Al~]lCl^ 
Is there any difference in the quantivalence of Fe in the two com- 
pounds Fe=0 2 =CO and [Fe-Fe'jlO^SOJJ Answer the questions by 
the aid of graphic symbols. 

11. Is there any difference in the quantivalence of nitrogen in 
potassic nitrite K-O-NO and potassic nitrate K-0-N0 2 ? 

12. Represent by graphic symbols the difference between cyanic 
ether and cyanetholine (see problems 2 and 3 above). 

13. The symbol [## 2 ]C7 2 represents a single molecule, while 
Na. 2 Ck represents two molecules, and would be more properly writ- 
ten 2NaCl. W r hat is the difference in the two cases V 

14. Represent by the graphic method the symbols of potassic car- 
bonate KfOf(CO) and potassic oxalate K 2 =0 2 =(C 2 2 ), and show 
that both form a perfect molecular unit. 

15. Represent by the graphic method the following symbols ; 

Hi 2 =( C,H & ) (Propyl Glycol.) ; 
Bi Oi{ C 3 Ei 0) (Lactic Acid.) ; 



CHEMICAL TYPES. 79 

Ef 2 =( C 3 H, 2 ) (Malonic Acid) ; 
B.f 2 =( <7 3 8 ) (Unknown) , 

and thus show that they are formed after the same type. 

16. What is the atom-fixing power or quantivalence of the ele- 
ments and radicals, which appear in the various symbols given in 
this chapter ? Develop these symbols, and show that they repre- 
sent in each case a single perfect molecule. 

N. B. The student should practice developing the ordinary mole- 
cular symbols into the graphic forms described above, until he is per- 
fectly familiar with the method, and has acquired a clear conception 
of the different types of molecular structure. 



CHAPTER IX. 1 

BASES, ACIDS, AND SALTS. 

35. Hydrates, Alkalies, Bases. — It is not unfrequently the 
case that the technical terms of a science remain in use long 
after they have lost their original meaning. This is peculiarly 
true of those which we have placed at the head of this section. 
They have, with the exception of the first, come down to us 
from the period of alchemy, and are still retained in the lan- 
guage of trade and in many works on practical science, with a 
peculiar meaning which they have acquired during the last 
hundred years under the teaching of the dualistic theory. 
Since they, in many cases at least, suggest erroneous concep- 
tions in regard to the constitution of chemical compounds, it 
would be well if they could be discarded altogether ; but, as 
this is impracticable, we must endeavor to give to them as 
definite a meaning as possible. 

The term "hydrate" is applied to a class of compounds which 
were formerly supposed to contain waiter as such, but which are 
now believed to have no closer relation to water than is indi- 
cated by the circumstance that they have the same type, and 
may be formed from water by replacing one of its hydrogen 
atoms with some metal. Thus, by acting on water with potas- 
sium, we obtain potassic hydrate ; or, if we use sodium, we ob- 
tain sodic hydrate. 



2H-0-H -f KK=1KO-H -f H-H 

Water. Potassium. Potassic Hydrate. Hydrogen Gas. 

2HO-H+ Na-Na = 2 Na-O-H + H H 

Water. Sodium. Sodic Hydrate. Hydrogen Gas. 



[42] 



Both of these hydrates, and also those of the very rare but 
closely allied metals, lithium, esesium, and rubidium, are very 

1 In studying this chapter the student should endeavor to remember the 
names and symbols of the different compounds mentioned. Hitherto we 
have been chiefly employed with the forms of the symbols, and this exercise 
of the memory has not been expected. 



BASES, ACIDS, AND SALTS. 81 

soluble in water, and yield solutions which corrode the skin, and 
convert the fats into soaps. To all the substances known to 
them which possessed these caustic qualities the alchemists 
gave the name of alkalies, and this term is now applied to the 
five hydrates just enumerated. The first two of these are 
commercial products, and have important applications in the 
arts. They all differ from the hydrates of other metals in that 
they cannot be decomposed by heat alone. 

Again, if we act on water with calcium or magnesium, we 
obtain calcic or magnesic hydrate ; but the double atom of 
water is then decomposed by these bivalent metals. 



H 2 =0?H 2 + Ca = Car-O./H, + HH 

Water. Calcium. Calcic Hydrate. Hydrogen Gas. 

Hf0.fff 2 -f Mg — Mq-O.rH, + H-H 

Water. Mafmesinm. Mnfmpsin 1 fv-flrntp. TTvtlmtrpn i 



[43] 



Magnesium. Magnesic Hydrate. Hydrogen Gas. 

These two hydrates, as well as those of the allied metals, 
barium and strontium, although much less soluble in water 
than the alkalies, still dissolve in this common solvent to a 
limited extent, and manifest decided caustic qualities. When 
dry they have an earthy appearance, and hence are frequently 
known as the alkaline earths. They also differ from the true 
alkalies in the fact that they are readily decomposed by heat ; 
and since they are then resolved into water and a metallic 
oxide, as the following reaction shows, the opinion formerly 
entertained in regard to their composition was not unnatural. 

Mg* Of H 2 = MgO + J3 3 [44] 

When heated. 

Moreover, when the anhydrous oxides are mixed with water, 
they enter into direct union with a portion of the liquid. This 
combination is usually attended with the evolution of great 
heat, and the process is known as slaking. 

Ca + H t = Ca- OfH 2 . [45] 

There are many other metallic hydrates which are still more 

readily decomposed by heat. These, as a rule, cannot be 

formed by the direct union of the corresponding metallic oxide 

and water, but may be obtained by adding to a solution of 

6 



82 BASES, ACIDS, AND SALTS. 

a salt of the metal one of the soluble hydrates mentioned 



tCuCk + 2JSTa-0-JI+ Aq) = (Cu=0. r H 2 + 2NaCl-\-Aq) 

Cupric Chloride. Cupric Hydrate. Sodic Chloride. 

[46] 
(ZnCL + 2K-0-H+Aq) = (Zn-OfH., + 2KCI + Aq) 

Zincic Chloride. Zincic Hydrate. Potassic Chloride. 



[Fe^Cl 6 +3Ba--0,=H 2 +Aq)=([Fe.^Wm+3BaC/ 2 +Aq) 

erric Chloride. Ferric Hydrate. Baric Chloride. 



The hydrates are regarded by some chemists as compounds 
of the metal with the compound radical hydroxyl, and their 
symbols are then written after a simpler type, thus, — 

Ca-(HO) 2 Fe-(HO) 2 [_c\ 2 J(HO) & 

Calcic Hydrate. Ferrous Hydrate. Chromic Hydrate. 

Ammonia. — Closely allied to these metallic hydrates is a 
very remarkable compound, formed by dissolving ammonia 
gas, NH& in water. Although the product resembles, in many 
of its physical relations, a simple solution of gas in water, yet 
the compound in all its chemical relations acts like a metallic 
hydrate, 

jyff s + H 2 = NH.-O-H 

Ammonia Gas. Water. Ammonic Hydrate. 

which has led chemists to write its symbol after the type of 
water, and to assume the existence of a univalent compound 

radical NH^ to which has been given the name of ammonium. 
Metallic Oxides or Basic Anhydrides. — Closely allied to 
the metallic hydrates, in the relation we are now considering, 
are many of the simple compounds of the metals with oxygen 
which are called in general metallic oxides. Such compounds 
as 

Ca=0 BaO Pb=0 Fe-0 Cu-0 Ag 2 =0 

Calcic Oxide. Baric Oxide. Plumbic Oxide. Ferrous Oxide. Cupric Oxide. Argentic Oxide. 

may be regarded as formed from one or more molecules of water, 
by replacing all the atoms of hydrogen with those of some metal ; 
and these oxides as well as the hydrates before mentioned are 
frequently classed together under the common title of bases, 
although it would be best to confine this term to the metallic 



BASES, ACIDS, AND SALTS. 83 

hydrates alone, and to distinguish the basic oxides as basic 
anhydrides. (37) 

Salts. — The atoms of hydrogen still remaining in a metallic 
hydrate may be replaced with the atoms of a well-defined class 
of non-metallic elements and compound radicals ; and, for a 
reason which will soon appear, the replacing atoms are called 
acid or negative radicals. 1 

From this replacement results a new class of compounds we 
call salts. Thus, — 

KO-H gives K-O-Cl, also KO-N0 2 and K~0-(C 2 H: 3 0) 

Potassic Hydrate. Potassic Hypochlorite. Potassic Nitrate. Potassic Acetate. 

Ca--0rH 2 gives Ca--0.fSO, Ca-O./CO Ca=0 2 =(CM 3 0) 2 

Calcic Hydrate. Calcic Sulphate. Calcic Carbonate. Calcic Acetate. 

36. Acids. — Opposed in chemical properties to the so- 
called bases is another very important class of compounds 
called acids. They derive their name from the fact that ihey 
are generally soluble in water and have a sharp or sour taste, 
although there are many exceptions to the rule. Like the 
bases, they all contain hydrogen ; but this hydrogen can no 
longer be replaced by non-metallic elements or negative radi- 
cals, but only by metallic elements and positive radicals, and it 
is herein that the chief distinction lies. Moreover, the opposi- 
tion of these two classes of compounds also appears in the fact 
that, while in bases the replaceable hydrogen atoms are united 
to a metallic atom or positive radical, which for this reason we 
frequently call a basic radical, in the acids, on the other hand, 

. ! The word radical, as used in chemistry, stands for any atom or group of 
atoms, which is, for the moment, regarded as the principal constituent of the 
molecules of a given compound, and which does not lose its integrity in the 
ordinary chemical reactions to which the substance is liable. The distinc- 
tion between basic and acid radicals (or positive and negative radicals as they 
are more frequently called) will become clear as we advance. It is sufficient 
for the present to state that, although these terms imply an opposition of rela- 
tions rather than a difference of qualities, yet, as a general rule, the metallic 
atoms are basic radicals, while the non-metallic atoms are acid radicals. 
Moreover it may be added, that among compound radicals those consisting of 
carbon and hydrogen alone are usually basic, and those containing also oxy- 
gen usually acid; and, further, that of the two most important radicals con- 
taining nitrogen, ammonium (NH 4 ) is strongly bnsic, and cyanogen ( CN) as 
decidedly acid. In this book, with few exceptions, the basic radicals are 
always placed on the left-hand, and the acid radicals on the right-hand side, 
of the molecular symbols. 



84 BASES, ACIDS, AND SALTS. 

these same hydrogen atoms are united as a rule to a non- 
metallic atom or negative radical, frequently, also, .called as 
above an acid radical. In most cases there is a vinculum 
which unites the two parts of the molecule ; and both in acids 
and in bases this vinculum consists usually of one or more 
oxygen atoms, although in a large class of acids the hydrogen 
atoms are united directly to the radical without any such con- 
nection. The acids of this class have by far the simplest 
constitution ; and we will give examples of these first, adding 
in each case a reaction to illustrate the acid relations of the 
compound. In studying these reactions, it must be borne in 
mind that the evidence of acidity is in each case to be found in 
the fact that one or more of the hydrogen atoms of the com- 
pound may be replaced by positive radicals or metallic atoms. 
This replacement may be obtained in one of four ways, — by 
acting on the acid, either with the metal itself, or with a metallic 
oxide, or with a metallic base, or with a metallic salt. 

(2HCI + Aq) + NaNa = (2 Na CI + Aq) + HI-HI 

Hydrochloric Acid. Sodium. Sodic Chloride. 

(2BCl + Aq) -f ZnO = (Znd 2 + H 2 + Aq) 

Zincic Oxide. Zincic Chloride. 

[47] 
(HBr + K-O-O + Aq) — (KBr + O. 2 + Aq) 

Hydrobromic Acid. Potassic Hydrate. Potassic Bromide. 

(BI+ Ag-0~NOi + Aq)= Agl + (H : 0-N0 2 -\-Aq) 

Hydriodic Acid. Argentic Nitrate. Argentic Iodide. Nitric Acid. 

We will next give examples of more complex acids, in which 
the two parts of the molecule are united by a vinculum of oxy- 
gen atoms. 

(H-0-(C,H s O) + NarO-H-\- Aq) = (Na-0-(C 2 H 3 0) -f H 2 O-f- A q) 

Acetic Acid. Sodic Hydrate. Sodic Acetate. 

(H 2 =0 2 =SO, + Aq) + CuO = (Cu=0<rS0 2 -f H,0 + Aq) 

Sulphuric Acid. Cupric Oxide. Cupric Sulphate. 

(HfOfPO -f SK-O-H -f- Aq) = (Kf.OfPO+SHiO + 'Aq) 

Phosphoric Acid. Potassic Hydrate. Potassic Phosphate. 

Such acids as these are called oxygen acids. Like the 
hydrates, they may be regarded as compounds of hydroxyl, 
but with negative instead of positive radicals, thus : — 



BASES, ACIDS, AND SALTS. 85 

HO-N0. 2 {HO).rS0. 2 (HO\fPO. 

Nitric Acid. Sulphuric Acid. Phosphoric Acid. 

This mode of writing the symbols is not only frequently con- 
venient, but has been of real value by bringing out unex- 
pected and important relations. It does not, however, indicate 
any fundamental difference of opinion in regard to the consti- 
tution of these hydrates, and this at once appears when the 
symbols are put into the graphic form. 

When an acid, like acetic acid, contains but one atom of hy- 
drogen, which is replaceable by a metallic atom or a positive 
radical, it is called monobasic; when, like sulphuric acid, it con- 
tains two such hydrogen atoms, it is called dibasic; when, like 
phosphoric acid, it contains three, it is tribasic, &c. Moreover, 
one evidence of this difference of basicity is found in the fact 
that whereas a monobasic acid can only form one salt with a 
univalent radical, a dibasic acid can form two, and a tribasic 
three. Thus, while we have only one sodic nitrate, there are 
two sodic sulphates and three sodic phosphates. 

Na-ON0. 2 KJta=-OfPO 

Sodic Nitrate. Acid Sodic Phosphate. 

H,Na=0. r SO, BNaiOfPO r . ft . 

Acid Sodic Sulphate. Neutral Sodic Phosphate. L'** J 

Na.rO.fSOo Ni^OfPO 

Neutral Sodic Sulphate. Basic Sodic Phosphate. 

There is, however, but one calcic sulphate, for, since the cal- 
cium atoms are bivalent, a single one is sufficient to replace 
both of the hydrogen atoms in the acid. 

37. Acid Anhydrides. — Besides the acids properly so called, 
all of which contain hydrogen, there is another class of com- 
pounds which bear the same relation to the true acids which the 
metallic oxides bear to the true bases. To avoid confusion, com- 
pounds of this class have been distinguished as anhydrides? and 
they may be regarded as one or more molecules of water in 
which all the hydrogen has been replaced by negative or acid 
radicals. As among the most important of these we may 
enumerate Sulphuric Anhydride SO.fO or S0 3 , Nitric Anhy- 

1 More precisely acid anhydrides, but as the basic anhydrides are usually- 
called simply metallic oxides, the qualifying term is seldom added. 



86 BASES, ACIDS, AND SALTS. 

dride (JST0 2 ) 2 =0 or JST 2 5 , Carbonic Anhydride 00=0 or 00 2 , 
Phosphoric Anhydride (P0 2 ) 2 =0 or P 2 5 , and Silicic Anhy- 

IV 

dride Sl=0 2 . Most of the anhydrides unite directly with 
water to form acids, and several of the acids, when heated, 
give off water and are resolved into anhydrides. [Compare 
44 and 45.] 

H 2 + SO, = B 2 =0./S0 2 

3B 2 + P 2 5 = 2B 3 =0 3 =PO 

[49] 
HfO^Si = SiO, + 2H 2 

Silicic Acid. Silicic Anhydride. 

2Hf0fB = B 2 3 + 3B 2 

Boric Acid. Boric Anhydride. 

Moreover in many cases these anhydrides will combine di- 
rectly with the metallic oxides to form salts ; and the reac- 
tions are best indicated by a rational formula, which represents 
the oxide and anhydride as radicals in the resulting compound. 
Thus, baric oxide burns in the vapor of sulphuric anhydride, 
yielding baric sulphate ; and lime also unites directly with the 
same anhydride, although with less energy, forming calcic sul- 
phate. 

BaO + S0 3 = BaO, S0 3 and CaO + S0 3 = CaO, S0 3 

We are thus led to the old formulae of the dualistic system, 
according to which the metallic oxides were the only true 
bases, the anhydrides were the only true acids, and the two 
were regarded as paired in all true salts. But, although in 
its modern theories our science has fortunately left the ruts to 
which the dualistic ideas for so long limited its progress, yet it 
must be remembered, that, according to our present definitions, 
these dualistic formulas are perfectly legitimate, and still give 
the simplest exposition of a large number of important facts. 

38. Salts. — The definition of the term "salt" has been clearly 
implied in the definitions of " base " and " acid " already given. 
It is any acid in which one or more atoms of hydrogen have 
been replaced with metallic atoms or basic radicals; it is any 
base in which the hydrogen atoms have been more or less re- 
placed by non-metallic atoms or acid radicals ; or it may be the 



BASES, ACIDS, AND SALTS. 87 

product of the direct union of a metallic oxide and an anhy- 
dride. A neutral salt is, properly speaking, one in which all 
the hydrogen atoms, whether of base or acid, have been re- 
placed as just stated. A basic salt is one in which one or 
more of the hydrogen atoms of the base remain undisturbed, 
and therefore still capable of replacement by acid radicals. An 
acid salt is one in which one or more of the hydrogen atoms of 
the acid remain undisturbed, and therefore capable of replace- 
ment by basic radicals. 

But, besides the basic and acid salts, which come under these 
definitions, there are also others which can be most simply de- 
fined as consisting of several atoms of the metallic oxide to one 
of anhydride, or of several atoms of anhydride to one of the 
metallic oxide. 

As an example of acid salts of the second class we have, be- 
sides the two sodic sulphates mentioned on page 85, also a 
third, which may be written JVa 2 0,2S0 3 . This is easily ob- 
tained by simply heating the acid sulphate. 

2(H, Na-O.rSOj = Nn,0. 2SO ;i -f IJI/D [50] 

Acid Sodic Sulphate. Sodic Bisulphate. Watur. 

If heated to a still higher temperature, one atom of the anhy- 
dride is set free, and the salt fails back into the neutral sul- 
phate. 

Na,0< 2S0 3 = Na 2 0,SO, + S£>, 

Bisulphate. Neutral Sulphate. Anhydride. 

This reaction justifies the dualistic form given to the symbol; 
but other relations of the bisulphate may be better expressed 
by the following typical formula, — 

2?a.fOf(SOrO-S0. 2 ) = m.fOrSO, + so, 

Sodic Bisulphate. Neutral Sulphate. Anhydride. 

in which a group of two atoms of S0 2 , soldered together by 
one atom of oxygen, acts as a bivalent radical. 

As an example of a basic salt of the second class we have, 
in addition to the two plumbic acetates of the normal type, 

Pb-0. r {C,ff 3 0) 2 and Pb=0.f{CJL,0), H 

Neutral Plumbic Acetate. Basic Plumbic Acetate. 



88 BASES, ACIDS, AND SALTS. 

a third salt containing three times as much lead, — 

(Pb-0-Pb-0-Pb)-~0.f(O 2 ff,O) 2 , [51] 

Triplumbic Acetate. 

in which a group of three atoms of lead, soldered together by 
two atoms of oxygen, acts as a bivalent radical. It is evident 
that, theoretically, any number of multivalent radicals might be 
united in this way, and also that the complex radical thus 
formed will have a quantivalence easily determined by esti- 
mating the number cf bonds which remain unsatisfied ; but, 
practically, the grouping cannot be carried to a very great ex- 
tent, for the stability of the radical diminishes with its com- 
plexity, and a condition is soon reached when it can no longer 
sustain, if we may so express it, its own weight. Moreover, 
while some radicals, like the atoms of lead, copper, mercury, 
and iron, are prone to group themselves in this way, the larger 
number show but little tendency to this mode of union. 

The symbols of these acetates may also be written on the 
dualistic type, which represents them as compounds of plumbic 
oxide, PbO, and acetic anhydride, €^^0^. We have, then, — 

PbO, C+fl.Os and 3PbO, C 4 ff G 3 [52] 

Neutral Plumbic Acetate. Triplumbic Acetate. 

and we may thus best illustrate the important fact that the 
second compound is prepared by combining with the first an 
additional quantity of plumbic oxide. 

It will appear on reviewing the symbols of the acids, bases, 
and salts given in this section, that, in by far the greater num- 
ber, the two parts of the molecule are held together by one or 
more atoms of oxygen, which act as a vinculum. Such com- 
pounds are called oxygen salts, using the word salt, as is fre- 
quently done, to stand for acids and bases, as well as for the 
true metallic salts ; and in fact they all belong to the same 
type of chemical compounds. Since oxygen plays so impor- 
tant a part in terrestrial nature, we might well expect that 
these oxygen compounds would hold a very conspicuous place 
in our chemical science, — and such is indeed the fact. Dur- 
ing the dualistic period the study of chemistry was almost 
wholly confined to the oxygen compounds, and, even now, 
they occupy by far the largest share of a chemist's attention. 



BASES, ACIDS, AND SALTS. 89 

There is, however, another element, namely, sulphur, which 
is capable of filling the place occupied by oxygen in many 
of its compounds, and thus may be formed a distinct class of 
bodies which are called sulphur salts. These compounds are 
not nearly so numerous as the oxygen salts, and have not been 
so well studied, so that a few examples will be sufficient to 
illustrate their general composition, and the relations which 
they bear to the corresponding oxygen compounds. 

Oxygen Salts. Sulphur Salts. 

BOB B-S-B 

Water or Hydric Acid. Sulphohydric Acid. 

K-O-B K-S-B 

Potassic Hydrate. Potassic Sulphohydrate. 

KrOrCO KfS/CS 

Potassic Carbonate. Potassic Sulphocarbonate. 

39. Test-Papers. — The soluble bases and acids, when dis- 
solved in water, cause a striking change of color in certain 
vegetable dyes, and these characteristic reactions give to the 
chemist a ready means of distinguishing between these two 
important classes of compounds. The two dyes chiefly used 
for this purpose are turmeric and litmus, and strips of paper 
colored with the dyes are employed in testing. Turmeric 
paper, which is naturally yellow, is turned brownish red by 
bases, while litmus paper, which is naturally blue, is turned 
red by acids, and in both cases the natural colur is restored by 
a compound of the opposite class. 

If to a solution of a strong base, like sodic hydrate, we add 
slowly and carefully a solution of a strong acid, like sulphuric, 
we shall at last reach a condition in which the solution affects 
neither test-paper, and it is then said to be neutral. On evap- 
orating this solution we obtain a neutral salt, like sodic sulphate, 
and the presence in the solution of the slightest excess of acid 
or base beyond the amount required to form this salt would 
have been made evident by the test-papers. In such cases, we 
may therefore use these test-papers to distinguish between acid, 
basic, and neutral salts, but only with great caution ; for we find 
that when, as in acid-carbonate of soda, a strong base is asso- 
ciated with a weak acid, the reaction is still basic, although 



90 BASES, ACIDS, AND SALTS. 

the acid may be greatly in excess, and, on the other hand, 
when, as in cupric sulphate, a weak base has been associated 
with a strong acid, the reaction may be strongly acid even in 
the basic salts. The explanation of these apparent anomalies 
is to be found in the fact that these colored reagents are all 
salts themselves, and the reactions examples of metathesis. 
The coloring matter of these dyes is an acid which varies its 
tint according as the hydrogen atoms have or have not been 
replaced ; and when, for any reason, the acid or base of the salt 
examined is not in a condition to determine the necessary me- 
tathesis, the characteristic change of color does not take place. 

Unfortunately, the facts just stated have led to great confu- 
sion in the use of the words "acid" and "basic" as applied to 
salts, since these terms sometimes have reference solely to the 
number of atoms of hydrogen, in the acid or base, which have 
not been replaced in the formation of the salt, and at other times 
refer to the reactions of the salt on the colored reagents just 
described. A confusion of this sort must have been noticed in 
the names of the three phosphates of soda on page 85. The 
so called neutral phosphate is theoretically an acid salt, and 
the basic phosphate a neutral salt, but the salts give with test- 
papers the reactions which their names indicate. The theo- 
retical is the only legitimate use, and the one we shall adhere 
to in this book, except in regard to names of compounds which 
cannot be arbitrarily changed. 

40. Alcohols, Fat Acids, Ethers. — The hydrocarbon radicals 
mentioned in § 34 yield a very large number of compounds 
after the type of water, which are closely allied to the hy- 
drates and anhydrides, both acid and basic, just described. If 
one of the hydrogen atoms in the molecule of water is replaced 
by either of the univalent basic radicals, methyl, ethyl, propyl, 
&c, we obtain a class of compounds, called alcohols, of which 
our common alcohol is the most important. On the other 
hand, if the atom of hydrogen is replaced by one of the uni- 
valent acid radicals, formyl, acetyl, propionyl, &c, we obtain an 
important class of acid compounds, of which acetic acid (vine- 
gar) is the be-t known, but which also includes a large number 
of fatty substances closely related to our ordinary fats. Hence 
the name Fat Acids, by which this class of compounds is gen- 
erally designated. 



BASES, ACIDS, AND SALTS. 



91 



Basic Hydrates or Alcohols. 

Methylic Alcohol (wood spirits) CH^O-B. 

Ethylic Alcohol (common alcohol) C 2 H 5 -OH. 

Propylic Alcohol C z H f O-H. 

Buty lie Alcohol C^HfO-K 

Amylic Alcohol (fusel oil) C 5 H 1]r O-H. 

(With six others already known.) 

Acid Hydrates, Fat Acids. 
Formic Acid E-O-CHO. 

Acetic Acid H~ 0- C 2 IT 3 0. 

Propionic Acid H-0-C s H 5 0. 

Butyric Acid H~0-C 4 B 7 0. 

Valerianic Acid H- O C 5 H 2 0. 

(With fifteen others already known.) 

If now we replace both of the hydrogen atoms of water by 
the same basic radicals mentioned above, we obtain a class of 
compounds called ethers, which correspond to the metallic 
oxides or basic anhydrides ; and if we replace the two hydro- 
gen atoms by the corresponding acid radicals, we obtain a 
similar series of acid anhydrides. Lastly, if we replace one of 
the hydrogen atoms by a basic radical, and the other by an 
acid radical, we get a class of compounds also called ethers 
(but distinguished as compound ethers), which correspond to 
the salts. 

Examples of Anhydrides. 
1. Simple Ethers. 

Methylic Ether CE :f O-CH 3 or (CH,). 2 =0. 

Ethylic Ether (common ether) C 2 H,-0~C,H 5 or (C,H 5 ).fO. 



Methyl-ethyl Ether 
Ethyl-amyl Ether 



2. Mixed Ethers. 

CH,-0-C,H,. 
C 2 H 5 -0-C 5 H n . 



3. Compound Ethers. 
Acetic Ether C 2 B 5 ~0-C 2 B 3 0. 

Butyric-methyl Ether CH S - - c[H- t 0. 

4. Acid Anhydrides. 
Acetic Anhydride C 2 H 3 0-0-C 2 H,0 or ( C,H,0).fO. 

Valerianic Anhydride C 5 H»0-0-C 5 H»0 or (C 5 H 9 0).fO. 



92 



BASES, ACIDS, AND SALTS. 



The positive radicals, of which the alcohols consist, hold an 
intermediate position between the strong basic radicals on the 
one hand, and the strong acid radicals on the other, and the 
same is true of the alcohols themselves, which hold a middle 
place between the strong basic and the strong acid hydrates. 
This is indicated by the following reactions ; in what way it is 
left to the student to inquire. 

2R-0-0 2 H 5 + K-K— 2K-0-C 2 H 5 + H-H 

2 CH f O-H+ Hr0.fS0 2 = {CH^f0.fS0 2 + 2 H 2 

41. Glycols. — The class of hydrates described in the last sec- 
tion belong to the simple type of water. But we have also a class 
of analogous compounds belonging to the type of water doubly 
condensed. If in the double molecule of water {Hr0.jrH 2 ) w T e 
replace one of the pairs of hydrogen atoms by either of the 
bivalent positive radicals, ethylene, propylene, butylene, &c, 
we obtain a series of compounds closely resembling the alco- 
hols, called glycols, and by substituting the related negative 
radicals we obtain two series of acid hydrates, which stand in 
the same relation to the glycols that the fat acids bear to the 
alcohols. These relations are shown in the following scheme, 
which, however, includes only the five first members of each 
of these three series of compounds. It should be noticed in 
this connection that each of the bivalent positive radicals yields 
two related negative radicals, while the univalent positive radi- 
cals of the last section yield only one such negative radical ; 
and moreover that the acids in the first series, although dia- 
tomic, are only monobasic, while those in the second series are 
both diatomic and dibasic (43). 



C,HfOfH 2 

Ethylic Glycol. 


Rf0. r C,H,0 

Glycolie Acid. 


Rr0.fa,o 2 

Oxalic Acid. 


C,ff ir OrH 2 

Propylic Glycol. 


KfOfC-HtO 

Lactic Acid. 


RrOrC ? H 2 2 

Malonic Acid. 


C 4 H,= Orff 2 

Butylic Glycol. 


Oxybutyric Acid. 


Rr0.rC 4 ff A 2 

Succinic Acid. 


C 5 H^O.fH 2 

Amylic Glycol. 


KfO.rC^O 

Valerolactic Acid. 


B.fOrC,ff c ,0 2 

Pyrotartaric Acid. 


C,H v rOrH 2 

Hexyl Glycol. 


Hf0 2 =C G H w O 

Leucic Acid. 


RfOrC,H 8 2 

Adipic Acid. 



BASES, ACIDS, AND SALTS. 93 

Corresponding to these basic and acid hydrates we have 
also been able to obtain in several cases the basic and acid 
anhydrides, besides a very large number of compound ethers. 

42. Glycerines and Sugars. — In the alcohols one hydrogen 
atom from the original typical molecule {typical hydrogen) re- 
mains undisturbed. In the glycols there are two such h} r dro- 
gen atoms, and hence these compounds are frequently called 
diatomic alcohols. Our common glycerine is a triatomic alco- 
hol, and may be regarded as formed from a molecule of water 
trebly condensed (II 3 =0 3 =H s ), by replacing one of the groups of 
hydrogen atoms with the trivalent radical glyceryl (C :i B 5 ). It 
is probable that a large number of triatomic alcohols or glycer- 
ines may hereafter be obtained, but only two are now known. 

Propylic Glycerine (common glycerine) H 3 =O^G 3 H s . 
Amylic Glycerine H 3 =0 3 ^C 5 H^. 

From the glycerines we may derive acids, anhydrides, and 
compound ethers, bearing to each other the same relations as 
those derived from the alcohols of a lower order, but only a 
few of the possible compounds which our theory would foresee 
are yet known. The natural fats are compounds of glycerine 
with the fat acids, and it is probable that our common sugars 
are likewise derived from alcohols of a still higher order of 
atomicity. 

43. Atomicity and Basicity of an Acid. — By the atom- 
icity of a compound is meant the number of hydrogen atoms 
which it retains from the original typical molecule still unre- 
placed, and the use of this term with reference to the basic 
hydrates has been already abundantly illustrated in this chap- 
ter. In the case of the acids a distinction must be made be- 
tween atomicity and basicity, which is frequently important. 

The formula of every acid may be written on the type of one 

or more atoms of hydrochloric acid, as H n R n , in which H n stands 

for the replaceable atoms of hydrogen, and R n for all the rest 

of the atoms of the molecule, which may be regarded as forming 

a radical with an atomicity equal to the number of replaceable 

i ii in 

hydrogen atoms. The symbols H-N0 3 RrSO^ H 3 =PO± are 



94 BASES, ACIDS, AND SALTS. 

written on this principle. In each case the acid is said to 
have the atomicity of the radical. The basicity of the acid, 
on the other hand, depends, not on the total number of replace- 
able hydrogen atoms, but on the number which may be 
replaced by metallic atoms or basic radicals. As a general 
rule, it is true that the basicity is the same as the atomicity, 
but this is not always the case. Thus lactic acid is diatomic 
but monobasic, and the same is true of the other acids homol- 
ogous with it (page 92). 



4 h=( an, o 3 ) Na, h-{ aji. 5 3 ) &*, ( c 7 h :> 6y-( c 3 h 4 o 3 ) 

Lactic Acid. Sodic Lactate. Sodic Benzolactate. 



K CM,( C 3 H 4 3 ) C 2 H 5 , C 2 II 5 =( C 3 H,0 3 ) 

Potassic Ethyl-lactate. Diethylic-lactate. 



Only one atom of hydrogen can be replaced by a metallic 
radical, but a second may be replaced by either a negative or 
an alcoholic radical, as in the last three symbols, and in desig- 
nating the atoms, thus differently related to the molecular struc- 
ture, it is usual to call the first basic and the other alcoholic 
hydrogen. 

We might, in like manner, distinguish between the atomicity 
and the acidity of a base, but this distinction has not been found 
as yet to be of practical importance. 

44. Water of Crystallization. — Among the most striking char- 
acteristics of the class of compounds we call salts is their sol- 
ubility in water and their tendency on separating from it, 
in consequence of either the evaporation or the cooling of 
the fluid, to assume definite crystalline forms. These crys- 
tals, as a general rule, are complex crystalline aggregates of 
molecules of the salt and molecules of water. The water is 
held in combination by a comparatively feeble force, and may 
be generally driven off by exposing the salt to the temperature 
of 100° C, when the crystals fall to powder. Sometimes it es- 
capes at the ordinary temperature of the air, when the crystals, 
as before, fall to powder and are said to effloresce. It thus evi- 
dently appears that the water, although an essential part of the 
crystalline structure, is not inherent in the chemical molecule, 
and hence the name Water of Crystallization. The presence of 



BASES, ACIDS, AND SALTS. 95 

water of crystallization in a salt is expressed by writing after 
the symbol of the salt, and separated from it by a period, the 
number of molecules of water with which each salt molecule 
is associated. Thus we have 



FeSO A .lH,0 Mr 2 CO,A0ff 2 O 

Crystallized Ferrous Sulphate or Green Vitriol. Crystallized Sodic Carbonate or Sal Soda. 

The same salt, when crystallized, at different temperatures 
not unfrequently combines with different amounts of water of 
crystallization, the less amounts corresponding to the higher 
temperatures. Thus manganous sulphate may be crystallized 
with three different amounts of water of crystallization. We 
have 

MnSO^lKfi when crystallized below 6° C. 
MnSO^H^O " « between 7° and 20°. 

-MnSO^AHfi " " between 20° and 30°. 

The crystalline forms of these three compounds are entirely 
different from each other ; and this fact again corroborates the 
view that the molecules of water, while a part of the crystalline 
structure, are not a part of the chemical type of the salt. It 
will be well to distinguish the molecular aggregate, which the 
symbols of this section represent, from the simpler chemical 
molecules by a special term, and we propose to call them crys- 
talline molecules. While, however, there is little room for 
difference of opinion in regard to the relations in which the 
molecules of water stand to the structure of most crystals, there 
are cases where the condition is apparently far less simple, and 
where we find the water so firmly bound to the salt itself that 
it seems to form a part of its atomic structure. 

Questions and Problems, 

1. Analyze reactions [42]. Show what is meant by a metallic 
hydrate, and define the term alkali. Write the similar reactions 
which may be obtained with lithium, caesium, and rubidium. Name 
in each case the class of compounds to which the factors and pro- 
ducts belong. Also represent these reactions by graphic symbols. 

2. Analyze reactions [43]. State the distinction between an 
alkaline earth and an alkali, and write the similar reactions which 
may be obtained with barium and strontium. Name in each case 



96 BASES, ACIDS, AND SALTS. 

the class of compounds to which the factors and products belong. 
Also represent the reactions by graphic symbols. 

3. Analyze reactions [44] and [45], and write the similar reac- 
tions which may be obtained with either of the metals, calcium, 
strontium, barium, and magnesium. What theory of the constitution 
of the metallic hydrates do these reactions suggest V 

4. In what respects do the hydrates Ca= 2 = Il 2 and Mg = 2 =H 2 
differ from K-O-H and Na-O-H ? 

5. Analyze reactions [46], and show that the principal products 
must be regarded as hydrates. Name the class of compounds to 
which the other products and factors belong. 

6. State the third theory which is held in regard to the constitu- 
tion of the hydrates, and write the symbols of the different hydrates 
according to this view. Also bring these symbols into comparison 
with those of the same compounds written after the other two plans, 
and show by means of graphic symbols how far these forms are arbi- 
trary, and how far they represent fundamental differences. 

7. In what sense may the solution of ammonia gas in water be 
regarded as an hydrate ? Write reactions [46], using ammonic hy- 
drate instead of the hydrates of sodium, potassium, and barium. 

8. In what relation do the metallic oxides stand to the hydrates ? 
Define the term base. 

9. Define the term salt, and illustrate your definition by examples. 

10. Define the term acid. How does an acid differ from a me- 
tallic hydrate ? Is an acid necessarily an hydrate ? What two 
classes of acids may be distinguished ? 

11. What is the distinction between an acid and a basic radical. 
How are they related to the two hydrogen atoms of water ? As- 
suming that there is no difference between these two atoms in the 
original molecule of water, does not the replacement of one of the 
atoms by a radical of either class alter the relations of the second ? 
Is there not an analogy between these phenomena and those of 
magnetism ? 

12. Analyze reactions [47 et seq.], and point out the evidence of 
acidity in each case. 

13. Analyze the following reactions. 

K-O-H +HF == KF +H2O 

Ca-0 2 -H 2 + H.r0.rCO = Ca-O.fCO + 2H,0 
Gu-0.fH 2 + 2H-0-N0 2 = Cu = 0,= (NO.,) 2 + 2H 2 



BASES, ACIDS, AND SALTS. 97 

Na CI + H.f 0./S0 2 == H, JVa-0.fS0 2 + SK91 
ZNaCl + HfOfSO % = Na 2 =0 2 =S0 2 + 231(91. 

• Point out the different acids and bases. In what does the evidence 
of their acidity or basicity appear either in these or in reactions pre- 
viously given ? Show in each case how the replacement of the hy- 
drogen atoms is obtained, and illustrate the difference between the 
hydrogen atoms of an acid and those of a base. What two classes 
of acids may be distinguished ? 

14. Regarding the hydrates as compounds of hydroxyl, how can 
you define the acids and bases of this class ? 

15. Represent the composition of nitric, sulphuric, and phosphoric 
acid by graphic symbols, and show that the two modes of writing 
their symbols embody essentially the same idea. 

16. Hydrochloric acid, acetic acid, nitric acid, hydriodic acid, hy- 
drobromic acid, sulphuric acid, carbonic acid, and phosphoric acid 
have what basicity ? Point out, in the various reactions given in 
this chapter, the evidence in each case, and write the symbols of the 
possible sodic salts of the different acids. 

1 17. What class of compounds do the symbols S0 3 , N a O v P 2 & , 
CO v and Si0 2 represent ? By a comparison of symbols show how 
these compounds may be regarded as formed from water, and how 
they are related to the corresponding acids. To what class of com- 
pounds do they stand in direct antithesis ? 

18. Define the terms basic and acid hydrate ; basic and acid an- 
hydride, and compare reactions [49] with [44 and 45], 

19. Analyze the reaction, BaO -f SO s = BaO, SO r 

What reason may be urged for writing the symbol of bnric sulphate 
in this way V What was the theory of the dualistic system in 
regard to such compounds ? Represent the symbol by the graphic 
method, and seek to determine whether the dualistic form is compat- 
ible with the theory of molecular unity. 

20. The following symbols represent compounds of what class ? 
H-OH; ITfOfPO;Fe=OfII 2 ; 2H-(HO)\ (P0 2 ). f O; 
K-OH; Ca-0,=ff 2 ; C 2 H f O-H;2Na-0-H; (0&Q)fO\ 
HfQfSi ; H-0-N0 2 ; Hf 2 =S0 2 ; (Fe-Fe) l0 2 ;H- 0-C 2 ff 3 0; 
Ca.fOi-Si;K-0-N0 2 ', (C 4 H 9 )fO;2s T a 2 =0 2 =S0 2 ; C 2 E,0-C 2 H s O. 

7 



98 BASES, ACIDS, AND SALTS. 

Give in each case the name of the compound so far as you are able 
to infer it from examples previously given, and show how the sym- 
bol is related to that of water. 

21. Point out the acid basic and neutral salts among the com- 
pounds represented by the following symbols : — 

H.Na-OyCO IT,K=0 2 =(C 2 2 ) {Hg-0-Hg-0-Hg)-0. r S0 2 

Na 2 = OrC K f 0. f ( C 2 2 ) Wg-Hgy0 2 =(N0 2 )2 

E 2 , Gm Oi-Si Cu=0 2 =(N0 2 ), IT [Fe-Fe]W. 6 l(S0 2 ) 3 

BUO^{N0 2 ),H 2 H 2 , fcOMs K 2 =0 2 =(S0 2 0-$0 2 ). 

What two classes of basic salts may be distinguished ? Convert the 
symbols into the dualistic form. 

22. Analyze reactions [49 and 50], and show how far they justify 
the dualistic form given to the symbols. Repreoent the same reac- 
tions in the graphic form. 

23. What class of compounds do the following symbols represent ? 

Ag^-SfAs Ag-SSbS Ca=S/H 2 . 

Write the symbols of the corresponding oxygen compounds. 

24. Explain the theory of the colored test pipers, and the use of 
the terms acid and basic in connection with them. To what confu- 
sion does the double meaning of these terms sometimes lead ? 

25. The members of the series of alcohols stand in what relation 
to each other ? Does the same relation exist, between the members 
of the series of fat acids, glycols, &c. ? Find a general symbol, 
which will represent the composition of each of these classes of com- 
pounds. 

* 

26. In what relations do the alcohols stand to the fat acids, and the 
glycols to the acids derived from them ? 

27. Select examples from each of the classes of compounds de- 
scribed in sections 40, 41, and 42, and bring the symbols into com- 
parison with those of some simple hydrate or anhydride with which 
they exactly correspond. 

28. We are acquainted with a class of compounds known as con- 
densed glycols, one of which has the following symbol : — 

( 2 H f 0- C 2 H 4 - 0- C 2 H 4 ) - 0.fH 2 . 



BASES, ACIDS, AND SALTS. 99 

To what class of salts does this correspond ? 

29. Judging from the following symbols of a few of the salts of 
tartaric acid, what conclusion should you reach in regard to the 
atomicity and basicity of this acid ? 

■Bt*Of(CAOd\ KJIfO^(C,B 2 2 ); K 2J HfOf(C 4 ff 2 2 ); 

(C 2 R 5 ) 2 , H 2 m{ C,B 2 2 ) ; (C 2 ff 5 ) 2 , (C 2 ff 3 0)^0^(C,ff 2 2 ) 

30. What is the atomicity and basicity of the different acids 
whose symbols have been given in this chapter ? Does the basi- 
city of the different hydrocarbon acids (§ 40 to § 43) appear to 
have any connection with the number of oxygen atoms in the rad- 
ical ? 

31. How do you explain the state of combination of the water 
which enters into the composition of most crystalline salts? Show 
by an example how this mode of combination is represented sym- 
bolically. What facts may be adduced in support of the opinion 
that the molecules of water are not a part of the chemical type of 
the salt. 

Note. — Should the teacher think it best to introduce in this 
connection definitions of the several compounds formed after the 
type of ammonia gas, he will find them given in sections 166 to 171 
of Part II. ; and, if he finds it necessary, he should dwell more at 
length on the acids and salts of the type of hydrochloric acid than 
has been thought necessary in this chapter. 



CHAPTER X. 1 

CHEMICAL NOMENCLATURE. 

45. Origin of Nomenclature. — Previous to the year 1787 
the names given to chemical compounds were not conformed to 
any general rules ; and many of these old names, such as oil of 
vitriol, calomel, corrosive sublimate, red precipitate, saltpetre, 
sal-soda, borax, cream of tartar, Glauber's and Epsom salts, are 
still retained in common use. As chemical science advanced, 
and the number of known substances increased, it became 
important to adopt a scientific nomenclature, and the system 
which came into use was due almost entirely to Lavoisier, who 
reported to the French Academy on the subject, in behalf of a 
committee, in the year named above. In the Lavoisierian 
nomenclature the name of a substance was made to indicate its 
composition ; and at the time of its adoption, and for fifty years 
after, it was probably the most perfect nomenclature which 
any science ever enjoyed. It was based, however, on the 
dualistic theory, of which Lavoisier was the father ; and, when 
at last the science outgrew this theory, the old names lost much 
of their significance and appropriateness. Within the last few 
years the English chemists have attempted to modify the old 
nomenclature so as to better adapt the names to our modern 
ideas. Unfortunately the result, like most attempts to mend a 
worn-out garment, is far from satisfactory, although it is prob- 
ably the best which under the circumstances could be attained. 
The new nomenclature has not the simplicity or unity of the 
old, and its rules cannot be made intelligible until the student 
is more or less acquainted with the modern chemical theories. 
Fortunately, however, the admirable system of chemical sym- 
bols supplies the defects of the nomenclature, and for many 

1 In studying this chapter, the student is expected to remember the names 
corresponding to the different symbols, and also the symbols corresponding 
to the names. 



CHEMICAL NOMENCLATURE. 101 

purposes may be used in its place. "We have, therefore, devel- 
oped this system first, but have also used, meanwhile, the corre- 
sponding scientific names, so that the student might become 
familiar with the nomenclature, and gather its rules as he 
advanced. A brief summary of these rules is all that will be 
necessary here. 

46. Names of Elements. — The names of the elements are 
not conformed to any fixed rules. Those which were known 
before 1787, such as sulphur, phosphorus, arsenic, antimony, 
iron, gold, and the other useful metals, retain their old names. 
Several of the more recently discovered elements have been 
named in allusion to some prominent property or some circum- 
stance connected with their history: as oxygen, from dgvs 
yewdco (acid-generator) ; hydrogen, from vScop ycwdco (water- 
generator) ; chlorine, from ^Xcopd? (green) ; iodine, from Icodfjs 
(violet) ; bromine, from (Bpcbpos (fetid odor). The names of the 
newly discovered metals have a common termination, um, as 
potassium, sodium, platinum ; and the names of several of the 
newly discovered metalloids end in ine, as chlorine, bromine, 
iodine, fluorine. Equally arbitrary names have been given to 
the compound radicals ; but, with a few exceptions, they all 
terminate in yl or ene, as ethyl, acetyl, hydroxyl, and ethylene, 
acetylene, &c. 

47. Names of Binary Compounds. 1 The simple compounds 
of the elements with oxygen are called oxides, and the specific 
names of the different oxides are formed by placing before the 
word "oxide" the name of the element, but changing the termi- 
nation into to or ous, to indicate different degrees of oxidation, 
and using the Latin name of the element in preference to the 
English, both for the sake of euphony and in order to secure 
more general agreement among different languages. When 
the same element unites with oxygen in more than two pro- 
portions, the Greek numeral prefixes, di, tri, tetra, penta, &c, 
are added to the word " oxide," in order to indicate the addi- 
tional degrees. Formerly these compounds were called ox- 
ides of the different elements, the degrees of oxidation being 
indicated solely by the prefixes ; and, as the old names are still 
in very general use, they are also given in the following ex- 
amples : — 

1 Compounds of two elements. 



102 



CHEMICAL NOMENCLATURE. 





New Names. 


Old Names. 


AgO 


is Argentic Oxide 


or Oxide of Silver 


N 2 


" Nitrous Oxide 


" Protoxide of Nitrogen 


NO 


" Nitric Oxide 


" Deutoxide of Nitrogen 


NO, 


" Nitric Dioxide 


" Peroxide of Nitrogen 


FeO 


" Ferrous Oxide 


" Protoxide of Iron 


Fe 2 O s 


" Ferric Oxide 


" Sesquioxide of Iron. 



An exception to the above rules is sometimes made in the 
case of those oxides which, when combined with the elements 
of water, form acids. As has been already stated, page 85, 
such compounds are called anhydrides, but the degrees of oxi- 
dation are distinguished as before, thus : — 







New Names. 




Old Names. 


so 2 


is 


Sulphurous Anhydride 


or 


Sulphurous Acid 


so t 


u 


Sulphuric Anhydride 


" 


Sulphuric Acid 


N 2 O s 


u 


Nitrous Anhydride 


a 


Nitrous Acid 


N 2 5 


u 


Nitric Anhydride 


u 


Nitric Acid 


P 2 3 


u 


Phosphorous Anhydride 


(( 


Phosphorous Acid 


P 2 o 5 


u 


Phosphoric Anhydride 


u 


Phosphoric Acid 


C0 o 


u 


Carbonic Anhydride 


(( 


Carbonic Acid 


Si0 2 


(( 


Silicic Anhydride 


u 


Silicic Acid. 



The names in common use, even among chemists, of the 
earths, the alkaline earths, and the alkaline oxides, make 
another important exception to the general rules given above, 
thus : — 



Al n 3 


Alurainic Oxide is commonly 


called 


Alumina 


BaO 


Baric Oxide " " 


<< 


Baryta 


SrO 


Strontic Oxide " " 


a 


Strontia 


CaO 


Calcic Oxide " " 


a 


Lime 


M< t O 


Magnesic Oxide " " 


u 


Magnesia 


K n O 


Potassic Oxide " " 


it 


Potassa 


Na 2 


Sodic Oxide " " 


a 


Soda. 



As this last class of oxides stands in the same relation to the 
bases in which the previous class stands to the acids, they have 
also been called by some chemists anhydrides. 

The names of the binary compounds of the other elements 
are formed like those of the oxides. 



CHEMICAL NOMENCLATURE. 



103 



Compounds of Chlorine 


are 


called 


Chlor?//es 


u 


it 


Bromine 


u 


" 


"Bromides 


a 


(( 


Iodine 


a 


a 


Iodides 


u 


n 


Fluorine 


a 


(c 


Fluorides 


It 


(i 


Sulphur 


a 


a 


Sulphides 


(( 


« 


Nitrogen 


« 


a 


Nitrides 


a 


it 


Phosphorus 


tt 


a 


Thosphides 


« 


a 


Arsenic 


a 


u 


Arsenides 


«c 


u 


Antimony 


a 


a 


AntimomV/es 


u 


it 


Carbon 


a 


u 


Carbonicles. 



Moreover, the specific names of the several compounds also 
follow the analogy of the oxides, thus : — 

Old Names. 
Protochloride of Tin 
Perch loride of Tin 
Subsulphide of Iron 
Protosulphide of Iron 
Sesquisulphide of Iron 
Bisulphide of Iron 
Fluoride of Calcium. 

Here, agiin, mu*t be noticed several exceptions to the gen- 
eral rule. Several simple compounds of the elements with hy- 
drogen, of which the hydrogen is easily replaced with a metal 
or positive radical, are called acids, and retain the specific 
names of the old nomenclature, thus : — 







New Names. 


SnCh 


is 


Stannous Chloride 


SnCl\ 


(< 


Stannic Chloride 


Fe n S 


a 


Di ferrous Sulphide 


FeS 


u 


Ferrous Sulphide 


FejS, 


u 


Ferric Sulphide 


FeS 2 


u 


Ferric Disulphide 


CaFl 


a 


Calcic Fluoride 



IICl or 


Ilvdric Chloride 


is 


called 


Hydrochloric Acid 


HBr " 


Ilvdric Bromide 


a 


tt 


Ilvdrobromic Acid 


HI " 


Hydric Iodide 


a 


u 


Hydriodic Acid 


HFl " 


Ilvdric Fluoride 


tt 


« 


Hydrofluoric Acid 


H 2 S " 


Hydric Sulphide 


a 


a 


Hydrosulphuric Acid. 



The last compound is frequently called also sulphuretted 
hydrogen, and several other hydrogen compounds are named 
after the same analogy, while others again are always called by 
their well-known trivial names, thus : — 



H 3 Sb is Antimoniuretted Hydrogen 

H r ls " Arscniuretted Hydrogen 

II.jP " Phosphuretted Hydrogen 

H^N " Ammonia Gas 

H A C " Marsh Gas or Light Carburetted Hydrogen 

H i C i " Olefiant Gas or, as a radical, Ethylene. 



104 CHEMICAL NOMENCLATURE. 

48. Ternary Compounds. — Of the old class of ternary 
compounds, it is only those which are formed after the type of 
water for which the rules of the nomenclature need at present 
be explained. 

49. Bases. — These we call simply hydrates, and for the 
specific name we take the name of the positive radical, chang- 
ing the termination into ic or ous, and using such prefixes as 
circumstances may require, thus : — 

New Names. Old Names. 

K-O-H is Potassic Hydrate or Hydrate of Potassa 

Ca=0 2 =H 2 " Calcic Hydrate " Hydrate of Lime 

Fe-0fH o « Ferrous Hydrate « {Hydrate of Pretax- 

" ( ide of Iron. 

FemH 6 " Ferric Hydrate « j Hydrate of Sesquiox- 



ide of Iron. 
ZoW^H± Zirconic Hydrate or Hydrate of Zirconia. 

50. Acids. — The inorganic acids all take their specific names 
from the name of the most characteristic element of the nega- 
tive radical, which is modified by terminations and prefixes as 
before, only the last are usually taken from the Greek rather 
than the Latin. Here the old and the new names coincide. 

H-O-NOn is called Nitric Acid 

H 2 =O z =S0 2 " " Sulphuric Acid 

Ho=Oo=SO " " Sulphurous Acid 

n 
HfOf(S-O-S) " " Hyposulphurous Acid 

The specific names of the organic acids are, as a rule, arbitrary, 
like tartaric acid, citric acid, malic acid, gallic acid, uric acid, 
and the like. 

51. Salts. — The name of a salt is formed from the name 
of the acid from which the salt is derived, preceded by the 
names of the basic radicals. "When the name of the acid ends 
in ic the termination is changed into ate, when in ons into ite. 
Moreover, the terminations ous and ic are retained in connec- 
tion with the name of the basic radical, and such prefixes are 
used as may be necessary for distinction, thus : — 



CHEMICAL NOMENCLATURE. 105 

New Names. Old Names. 

Ca=0 2 =CO is Calcic Carbonate or j Carbonate of 

( Lime 

Ca--Of(S-O-S) « Calcic Hyposulphite « Hyposulphite 

(of Lime 

Ba-0,=SO « Baric Sulphite « Su |P hite of 

r ( Baryta 

Fe-QfSO, « Ferrous Sulphate « Protosulphate 

( of Iron 

FeMO^SO.^ " Ferric Sulphate « ^sulphate of 

( Iron 

(iVT/J, Mg=0 3 =PO " Ammonio-magnesic Phosphate 

H,(NH^),Na=0.=PO " Hydro-ammonio-sodic Phosphate. 

#, Na&O&PQ « Hydro-disodic Phosphate. 

#4, Ca vi 6 vi (PO) 2 « Tetrahydro-calcic Diphosphate. 

NafOfB 4 5 " Disodic Tetraborate (Borax). 

Note. — The rules of the nomenclature given above conform to 
what the author regards as the best present use among chemists. 
There is, however, an important departure from the more general 
use, which must not be overlooked. Several English authors, who 
think that the adjectives derived from the Latin names of the ele- 
ments, with terminations in ic and ous, are not in harmony with 
English idioms, use such terms as Gold Chloride, Silver Nitrate, and 
Iron Sulphate, instead of Auric Chloride, Argentic Nitrate, and 
Ferrous Sulphate. This usage, however, appears to the writer open 
to equally just criticism, besides abridging greatly the capabilities of 
the nomenclature, which is full of similar incongruities. Nor does 
he sympathize with the same class of writers in rejecting the word 
** anhydride " as a part of the name of a substance, on the ground 
that it does not express its constitution, but only a mode of its deri- 
vation ; for a similar objection might be urged with equal force 
against the terms " acid " and " hydrate." Moreover, he lias thought 
it best, in a work designed chiefly for instruction, not only to intro- 
duce no novelties, but also to represent the actual usage, so far as 
possible, in all its phases. He would, however, offer the following 
suggestions as guides to the student in selecting for his own use a 
more uniform and consistent system, hoping that before long some 
agreement will be reached among chemists, by which greater uni- 
formity may be secured. He would recommend, — 



106 CHEMICAL NOMENCLATURE. 

First, that the terminations ic, ous, ate, and ite, with the modify- 
ing Greek and Latin prefixes, should be used so far as possible to 
distinguish the quantivalence of the chief multivalent radical of 
the compound. Secondly, that the Greek numeral prefixes should 
be used when necessary to indicate the number of atoms of any 
radical which each molecule of such compound contains. Thirdly, 
that in forming the name of a compound it should be the great 
object to indicate its composition, and that the use of such terms as 
acid, basic, or anhydride as parts of the name should be avoided, 
except when it is desired to make conspicuous the peculiar chemical 
relations which they expre-s. 

By referring to the list of sulphates on page 319, and to the list 
of sulphites on page 315, the student will find good examples of the 
application of these principles. He will notice that salts in which 
the quantivalence of sulphur is six are called sulplntes, while those 
in which it is four are called sulphites, and those in which it is two 
hyposulphites. Ag^in, on page 230 he will find the proper applica- 
tion of the term anhydrde explained, the term acid and basic hav- 
ing been already defined on page 82. 

Questions and Problems. 

1. Give the names of the compounds represented by the follow- 
ing symbols: — 

a. KCl\ K,0; K 2 S; KfO.fSO; K 2 =0 2 =S0 2 ; 
Kf0 2 =(S-0-S); 

b. FeOi Fe=0 2 =IT 2 ; Fe-0 2 -CO; Fe=0,= C 2 2 ; [Fe 2 ]W 3 ; 
Fe^O^H^ lFe 2 -\\0^{N0 2 \ 

c. H-Ch H-F; H-O-NOti H-O-NO; Hf0.fS0 2 \ 
R/OfSO; EfOfPQ. 

2. Write the symbols of the following compounds : 

a. Calcic Sulphide; Calcic Sulphite ; Calcic Hyposulphite; Cal- 
cic Sulphate; Calcic Hydrate; Calcic Sulphohydrate ; Calcic Car- 
bonate ; Calcic Sulphocarbonate ; Calcic Silicate. 

b. Water ; Potassic Hydrate ; Nitric Acid ; Potassic Nitrate ; 
Nitric Anhydride; Potassic Oxide. 

c. Magnesic Oxide ; Magnesic Hydrate ; Magnesic Nitrate ; 
Magnesic Carbonate ; Magnesic Phosphate ; Amuionio-magnesic 
Phosphate. 

N. B. Examples like the above should be greatly multiplied by 
the teacher, pains being taken to group together the names and 
symbols in the way best calculated to exhibit their relations and to 
assist the memory. 



CHAPTER XI. 

SOLUTION AND DIFFUSION. 

52. Solution. — The solvent power of water is one of the 
most familiar facts of common experience, and all liquids pos- 
sess the same power to a greater or less degree, but they differ 
very widely from each other in the manifestation of their 
solvent power, which for each liquid is usually limited to a 
certain class of solids. Thus mercury is the appropriate sol- 
vent of metals, alcohol of resins, ether of fats, and water of salts 
and of similar compounds of its own type. Water is by far the 
most universal solvent known, and for this reason, as well as 
on account of its very wide diffusion in nature, it becomes the 
medium of most chemical changes. The phenomena of aqueous 
solution form therefore a very important subject of chemical 
inquiry, and these alone will be considered in this connection. 

The solvent power of water, even on bodies of its own type, 
differs very greatly. Some solids, like potassic carbonate, or 
calcic chloride, liquefy in the atmosphere by absorbing the 
moisture it contains. Such salts are said to deliquesce, and are 
rendered liquid by a very small proportion of water. O.her 
salts, like calcic sulphate, require for solution several hundred 
times their weight of water, and others again, like baric sul- 
phate, are practically insoluble. 

As a general rule the solvent power of water increa-es with 
the temperature ; but here, again, we observe the greatest dif- 
ferences between different substances. While the solubility 
of some salts increases very rapidly with the temperature, that 
of others increases not at all, or only very slightly ; and there 
are a few which are actually more soluble in cold water than 
in hot. The solubility of each substance is absolutely definite 
for a given temperature, and we can determine by experiment 
the exact amount which 100 parts of water will in any case 
dissolve. The results of such experiments are best represented 
to the eye by means of a curve drawn as in the accompanying 
figure on the principles of analytical geometry. 



108 



SOLUTION AND DIFFUSION. 
Fig. 2. 




The figures on the horizontal line indicate degrees of tempera- 
ture, and those on the vertical line parts of salt soluble in 100 
parts of water. To find the solubility of any salt, for a stated 
temperature, the curve being given, we have only to follow up 
the vertical line corresponding to the temperature until it 
reaches the curve, and then, at the end of the horizontal line 
which intersects the curve at the same point, we find the num- 
ber of parts required. These curves also show in each case 
the law which the change of solubility obeys. 

When a liquid has dissolved all of a solid that it is capable of 
holding at the temperature, it is said to be saturated ; but when 
saturated with one solid the liquid will still exert a solvent 
power over others ; indeed, in some cases the solvent power is 
thereby increased. When several salts are dissolved together 
in water, a definite amount of metathesis seem* always to take 
place, and the different positive radicals are divided between 
the several acids in proportions which depend on the relative 
strength of their affinities, and on the quantities of each pres- 
ent. If in this way either an insoluble or a volatile product is 
formed, the solid or the gas at once falls out of the solution, 
and, the equilibrium being thus destroyed, a new metathesis 
takes place, and this goes on so long as any of these products 
can be formed. Here, then, we find a simple explanation of the 
two important laws already stated on page 37. 



SOLUTION AND DIFFUSION. 109 

53. Solution of Gases. — Most liquids, but especially water 
and alcohol, exert on gases a greater or less solvent power, 
which is marked by differences of manifestation similar to 
those we have already studied in the case of solids, although 
the peculiar physical conditions of the gas somewhat modify 
the result. Under the same conditions, the volume of gas dis- 
solved is always the same ; but it varies with the pressure of 
the gas on the surface of the liquid, with the temperature, and 
with the peculiar nature of the gas and the absorbing liquid. 
The quantity 1 of gas dissolved by one cubic centimetre of a 
liquid on which it exerts a pressure of 76 c. m. is called the 
coefficient of absorption. This coefficient, in almost every in- 
stance, diminishes with the temperature ; but, as in the case of 
solids, each substance obeys a law of its own, which must be 
determined by experiment. The observed values for several of 
the best known gases, when absorbed by water and alcohol, are 
given in the Chemical Physics, Table VII. With these data 
we can easily calculate the quantity of any of these gases which 
a given volume of water or alcohol will absorb, assuming that 
the gas exerts on the liquid a pressure of 76 c. m. Moreover, 
since the quantity of a gas absorbed by a liquid varies directly 
as the pressure which the gas exerts upon it, we can easily 
calculate from the first result the quantity absorbed at any 
given pressure. Again, it is a direct consequence of the last 
principle that at a fixed temperature a given mass of liquid will 
dissolve the same volume of gas, whatever may be the pressure. 
Lastly, if a mass of liquid is exposed to an atmosphere of 
mixed gases, it will absorb of each the same quantity as if this 
gas was alone present and exerting on the liquid the same 
partial pressure which falls to its share in the atmosphere. 
The amount dissolved of each gas is easily calculated when the 
partial pressure and the coefficient of absorption are known. 
It is thus that water absorbs the oxygen and nitrogen gases of 
our terrestrial atmosphere ; and the fact that these two gases 
are found dissolved in the ocean in very different proportions 
from those present in the atmosphere is a conclusive proof that 
the air is a mixture, and not, as was formerly supposed, a chem- 
ical compound. 

1 By quantity of gas is here meant the volume in cubic centimetres meas- 
ured under the standard conditions of temperature and pressure. 



110 SOLUTION AND DIFFUSION. 

54. Solution and Chemical Change. — There seems at first 
sight to be a wide difference between solution and. chemical 
change ; for, while in the first the solid body becomes diffused 
through the liquid menstruum wiihout losing its chemical 
identity or destroying that of the liquid, there is in the second 
a complete identification of the combining substances in the 
resulting compound. 

The same wide difference appears also between mechanical 
and chemical solution, which are sometimes confounded by 
students, because, unfortunately, the same term has been applied 
to both. When salt or sugar is dissolved in water, the 
differences between salt and solvent are preserved ; but when 
chalk is dissolved in hydrochloric acid, or copper in nitric acid, 
there is a complete identification of the differences in the 
resulting compound ; and the only ground for calling such 
chemical changes solution is the fact that the solution of the 
resulting salt in the water, used as the medium of the chemical 
change, is frequently an essential condition of the process. 

But if, instead of comparing extreme cases, we study the 
whole range of chemical phenomena, we shall find that the 
distinction is by no means so clearly marked. In many cases 
what seems to be a simple solution can be shown to be a mixed 
effect at least of solution and chemical combination ; and be- 
tween this condition of things, where the evidence of chemical 
combination is unmistakable, and a simple solution, like that of 
sugar in water, we have every degree of gradation. To such 
an extent is this true, that the facts seem to justify the opinion 
that solution is in every case a chemical combination of the 
substances dissolved with the solvent, and that it differs from 
other examples of chemical change only in the weakness of the 
combining force. 

The metallic alloys afford another striking illustration of the 
same principle. They are originally solutions of one metal in 
another ; but in many cases the result is greatly modified by 
the chemical affinities of the metals and their tendency to form 
definite chemical compounds. 

55. Liquid Diffusion. — Closely connected with the phe- 
nomena of solution are those of liquid diffusion. These phe- 
nomena may be studied in their simplest form, by placing an 
open vial filled with a solution of some salt in a much larger 



SOLUTION AND DIFFUSION. 



Ill 



Fig. 3. 




jar of pure water, as shown in Fig. 3, and so carefully arranging 
the details of the experiment that the surfaces of the two 
liquids may be brought in contact without mixing them me- 
chanically. It will then be found that the salt molecules will 
slowly escape from the vial and spread 
throughout the whole volume of the 
water. The rate of the diffusion in- 
creases with the temperature equally 
for all sub.-tances, and the whole phe- 
nomenon is probably caused by that 
same molecular motion to which we 
refer the effects of heat. At best, how- 
ever, the diffusion is very slow, as we 
should expect, considering the limited 
freedom of motion which the liquid 
molecules possess. It is found, also, that 
the rate of diffusion differs very greatly 

for the different soluble salts ; but these may be divided into 
groups of equidiffusive substances, and the rates of diffusion of 
the several groups bear to each other simple numerical ratios. 
If a mixture of salts be placed in the vial, it is found that the 
presence of one salt affects to some degree the diffusion of the 
other ; but if the difference of rate is considerable, a partial 
separation may be effected, and even weak chemical compounds 
may be thus decomposed- 

56. Crystalloids and Colloids. — There is a very great differ- 
ence of diffusive power between the ordinary crystalline salts 
(including most of the common acids and bases) and such sub- 
stances as gum, caramel, gelatine, and albumen, which are 
incapable of crystallizing, and which give insipid viscid solu- 
tions, readily forming into jelly ; hence the name colloids, from 
koWt), glue. The last class is distinguished by a remarkable 
sluggishness and indisposition to diffusion ; as is illustrated by 
the fact that sugar, one of the least diffusible of the crystalloids, 
diffuses seven times more rapidly than albumen, and fourteen 
times more rapidly than caramel. Our theories would lead us 
to believe that this great difference of diffusive power is caused 
by the fact that the molecules of colloids are far more complex 
atomic aggregates than those of crystalloids, and therefore are 
heavier and move more slowly. Moreover, the diffusive power 



112 SOLUTION AND DIFFUSION. 

is only one of many characters which point to a great molecu- 
lar difference between these two classes of substances. ■ 

57. Dialysis. — The difference of diffusive power between 
the two classes of compounds distinguished in the last section 
is still further increased when the aqueous solution is separated 
from the pure water by some colloidal membrane, and upon this 
fact Profes.-or Graham of London, to whom we owe our whole 
knowledge of this subject, has based a simple method of sepa- 
rating crystalloids from colloids, which he calls dialysis. 

A shallow tray is prepared by stretching parchment paper 
(which is itself an insoluble colloid) over one side of a gutta- 
percha hoop, and holding it in place by a somewhat larger hoop 
of the same material. The solution to be dialysed is poured into 
this tray, which is then floated on pure water whose volume 
should be eight or ten times greater than that of the solution. 
Under these conditions the crystalloids will diffuse through the 
porous septum into the water, leaving the colloids on the tray, 
and in the course of two or three days a more or less complete 
separation of these two classes of substances will have taken 
place. 

In this way arsenious acids and similar crystalloids may be 
separated from the colloidal materials, with which, in cases of 
poisoning, they are frequently found mixed in the stomach ; and 
by an application of the same method alumina, ferric oxide, 
chromic oxide, stannic, metastannic, titanic, molybdic, tungstic, 
and silicic acids have all been obtained dissolved in water in a 
colloidal condition. All these substances usually exist in a 
crystalline condition. The colloidal condition appears to be an 
abnormal state, and in almost all such substances there is a 
tendency towards the ciystalloid form. 

58. Diffusion of Gases. — Gases diffuse much more rapidly 
than liquids, as we should naturally expect from the greater 
freedom of motion which their molecules possess. Moreover, 
if the theory of the molecular condition of gases is correct, we 
ought to be able to calculate the relative rates of diffusion of 
different gases from their respective molecular weights. If it 
is true, as stated on page 13, that at any given temperature 

then it follows that 

V: V == \lhm! : \]± rn — ^n Or'. : t/Sp. Gr. 



SOLUTION AND DIFFUSION. 113 

Hence, if two masses of gas are in contact, the molecules of 
either gas must move into the space filled by the other with 
velocities which are inversely proportional to the square roots 
of the respective specific gravities. If one gas is hydrogen (Sp. 
Gr. = 1), and the other oxygen (Sp. Gr. — 16), the molecules 
of hydrogen must move past the section separating the two 
masses four times as rapidly as those of oxygen ; and, since all 
gas molecules occupy the same volume, it follows further that 
four volumes of hydrogen must enter the space filled by the 
oxygen, while one volume of oxygen is passing in the opposite 
direction Numerous experiments have fully confirmed this 
theoretical deduction, and the close agreement between theory 
and experiment furnishes important evidence in favor of the 
theory itself. Such experiments can be made, moreover, with 
great accuracy, since the molecular motion is not arrested 
by various porous septa, which may be used to separate the 
two masses of gas, and which entirely prevent the passage of 
gas currents that might otherwise vitiate the results. 



CHAPTER XII. 

RELATION OP THE ATOMS TO HEAT. 

59. The Atmosphere. — The earth is surrounded by an ocean 
of aeriform matter called the atmosphere, and many of the most 
important chemical changes which we witness in nature are 
caused by the reaction of this atmosphere on the substances 
which it surrounds and bathes. The great mass of the atmos- 
phere consists of the two elementary- gases, oxygen and nitro- 
gen, mixed together in the proportions indicated in the follow- 
ing table : — 

Air Composition Composition 

contains. By Volume. By Weight. 

Oxygen, 20.96 23.185 

Nitrogen, 79.04 76.815 

100. Too! 

That the air is a mixture, and not a chemical compound, is 
proved by the action of solvents upon it (§ 53) ; but, neverthe- 
less, the analyses of air collected in different countries, and at 
different heights in the atmosphere, show a remarkable con- 
stancy in its composition. Besides these two gases, which make 
up over 93 per cent of its whole mass, the air always contains 
variable quantities of aqueous vapor, carbonic anhydride, and 
ammonia, and sometimes also traces of various other gases and 
vapors. 

60. Burning. — Of the two chief constituents of the atmos- 
phere, nitrogen gas is a very inert substance, and serves chiefly 
to restrain its more energetic associate. Oxygen gas, on the 
other hand, is endowed with highly active affinities, and tends 
to enter into combination with other elementary substances, 
and with many compounds which are not already saturated 
with this all-pervading element. Many of these substances, 
such as phosphorus, sulphur, petroleum, coal, and wood, have 
such a strong affinity for oxygen, that, under certain conditions, 
they will absorb it from the atmosphere, and combine with it 



COMBUSTION. 115 

under the evolution of heat and light. These substances are 
said to be combustible, and the process of combination is called 
combustion. Moreover, all burning with which we are familiar 
in common life consists in the union of the burning body with 
the oxygen of the air. The chemical process in these cases 
may be expressed, like any other chemical reaction, in the form 
of an equation. 

Burning of Hydrogen Gas. 

Hydrogen Gas. Aque ous Vapor. 

2 mi-Hi + ®=® = 2 ZU 2 ®. [53] 



Burning of Carbon {Charcoal). 

Carbon. Carbonic Anhydride. 

<j + (oKo) — ®® 2 . [54] 



Burning of Benzole. 

Benzole. 

2®^ + 15®=® = 12@® 2 + 6 HI,®. [55] 



Burning of Alcohol. 

Alcohol. 

^H3 6 ® + 3®=® = 2@® 2 + 3HL®. [56] 



Burning of Sulphur. 

Sulphurous Anhydride. 

m + 2®=® = 2^® 2 . [57] 



Burning of Phosphorus. 

Phosphoric Anhydride. 

SP#S> a + 5®=® = 2 P 2 5 . [58] 



Burning of Magnesium. 

Masnesio Oxide. 

2 3Mg + ®=® = 2 JflgO. [59] 

The four substances, hydrogen gas, charcoal, benzole, and 
alcohol, may be regarded as types of our ordinary combustibles ; 
and, as the first four reactions show, the products of their com- 
bustion are aeriform. Moreover, these products are wholly 
devoid of any sensible qualities, and hence the apparent annihi- 



116 COMBUSTION. 

latioa of the burning substance, and the reason that for so long 
a period the nature of the process remained undiscovered. That 
these qualities of the products of ordinary combustion are not ne- 
cessary conditions of the process, but remarkable adaptations in 
the properties of those combustibles which are our artificial 
sources of light and heat, is shown by the fact, that, in the last 
two reactions, the products of the combustion are solids, while 
in [57] the product is a noxious suffocating gas. 

A careful inspection of the reactions will also teach the 
student several other important facts in regard to the processes 
here represented. It will be seen that, in the burning of 
hydrogen gas, two volumes of hydrogen gas and one volume 
of oxygen gas combine to form two volumes of aqueous vapor. 
It will further be noticed, that, in the burning of carbon and of 
sulphur, a given volume of oxygen gas yields in each case its 
own volume of the aeriform product. The carbon in the one 
case, and the sulphur in the other, are absorbed, as it were, by 
the gas, without any increase of volume. Further, if the ex- 
periments are made, which these reactions represent, it will 
appear that, in all those cases where the combustible is repre- 
sented as a gas, the combustion is accompanied by flame, while 
in the ca-e of carbon, which is a fixed solid, there is no proper 
flame. Hence we learn that flame is burning gas, and that 
only those substances burn with flame which are either gases 
themselves, or which, at a high temperature, become vola- 
tilized, or generate combustible vapors. Still other important 
facts connected with the process of combustion will be learned 
by solving the following problems according to the rules al- 
ready given (§§ 24 and 25). 

Problem. How many cubic centimetres of hydrogen gas, 
and how many of oxygen gas, are required to form one cubic 
centimetre of liquid water? 1 Ans. 1,240 cm 3 of hydrogen 
gas, and 620 c m of oxygen gas. 

Problem. How many cubic metres of air are required to 
burn 448 kilogrammes of coal, assuming that the coal is pure 
carbon? Ans. 833.333 m 3 of oxygen gas, or 3,975.83 m 3 of 
atmospheric air. 

1 Here, as in all other problems throughout the book, it is understood, unless 
otherwise expressly stated, that the measurements and weights are all taken at 
the standard temperature and pressure. (Compare §§ 10 and 13.) 



COMBUSTION. 117 

Problem. How many cubic metres of carbonic anhydride 
are formed by the burning of 1,000 kilogrammes of coal, as- 
suming, as before, that the coal is pure carbon ? Ans. 1,860. 

Problem. How many litres of carbonic anhydride, and 
how many of aqueous vapor, would be formed by burning one 
litre of benzole vapor ? Ans. Simple inspection of the equa- 
tion shows that 6 litres of the first and 3 litres of the second 
would be formed. 

Problem. How many litres of carbonic anhydride, and how 
many of aqueous vapor, would be formed by burning one litre 
of liquid alcohol (C^O) ? Sp. Gr. of liquid at 0° =z 0.815. 
Ans. One litre of alcohol weighs 815 grammes or 9,097 criths, 
and, since the Sp. Gr. of alcohol vapor is 23, this quantity of 
liquid would yield 395. G litres of vapor. Hence there would 
be formed 2 X 395.6 = 791.2 litres of carbonic anhydride, and 
3 X 395.6= 1,186.8 litres of aqueous vapor. 

61. Heat of Combustion. — The reactions of the last section 
represent only the chemical changes in the processes of burning. 
The physical effects which accompany the chemical changes 
our equations do not indicate, but it is these remarkable mani- 
festations of power which chiefly arrest the student's attention, 
and on this power the importance of the processes of combus- 
tion as sources of heat and light wholly depends. 

The immediate cause of the power developed in the process 
of combustion is to be found in the clashing of material atoms. 
Urged by that immensely powerful attractive force we call 
chemical affinity, the molecules of oxygen in the surrounding 
atmosphere rush, from all directions, and with an incalculable 
velocity, upon the burning body. The molecules of oxygen 
thus acquire an enormous moving power ; and when, at the 
moment of chemical union, the onward motion is arrested, 
this moving power is distributed among the surrounding mole- 
cules, and is manifested in the phenomena of heat and light. 1 
(Compare § 12.) 

1 According to our best knowledge, the phenomena of light are merely 
another manifestation of the same molecular motion which causes the phe- 
nomena of heat. When we speak of the amount of heat produced, we refer 
always to the total amount of molecular motion; although, even in the most 
brilliant illumination, the amount of mechanical power manifested as light 
appears to be inconsiderable as compared with that which takes the form of 
heat. 



118 COMBUSTION. 

The quantity of heat evolved during combustion "varies 
very greatly with the nature of the combustible employed, but 
it is always constant for the same combustible if burnt under 
the same conditions, and is exactly proportional to the weight 
of combustible consumed. We give in the following table the 
amount of heat evolved by one kilogramme of several of the 
most common combustibles when they are burnt in oxygen 
gas in their ordinary physical state. The numbers represent 
what is called the calorific power of the combustible. With 
the exception of the two last, which are only approximate 
values, they are the results of very accurate experiments 
made by Favre and Silbermann. 

Calorific Power of Combustibles. 

Units. Units. 

Hydrogen, 34,462 Sulphur, 2,221 

Marsh Gas, 13,063 Wood Charcoal, 8,080 

defiant Gas, 11,858 Carbonic Oxide, 2,400 

Ether, 9,027 Dry Wood (about), 3,654 

Alcohol, 7,184 Bituminous Coal, " 7,500 

The calorific power of our ordinary hydrocarbon fuels may 
be calculated approximately when their composition is known. 
Most of these combustibles contain more or less oxygen, and 
it is found, as might be expected, that the amount of heat 
developed by the perfect combustion of the fuel is equal 
to that which would be produced by the perfect combus- 
tion of all the carbon, and of so much of the hydrogen as 
is in excess of that required to form water with the oxygen 
present. The rest of the hydrogen may be regarded, so far 
as relates to the present problem, as in combination with oxy- 
gen in the state of water ; and in estimating the available heat 
produced, we must deduct the amount of heat required to con- 
vert, not only this water into steam, but also any hygroscopic 
water which may be present. Moreover, if we use in our cal- 
culation the value of the calorific power of hydrogen given in 
,the table above, we must also deduct the amount of heat re- 
quired to convert into vapor all the water formed in the process 
of burning, because, in the experiments by which this value 
was obtained, the aqueous vapor formed was subsequently con- 
densed to water and gave out its latent heat. 

Problem. Given the average composition of air-dried wood 
as in the table, to find the calorific power. 



Carbon, 400 

Hydrogen, 48 

Oxygen, 328 

Nitrogen and Ash, 24 
Hygroscopic Water, 200 
1000 



COMBUSTION. 119 

From the results of analysis we easily 

deduce 

Quantity of H in combination with O 41 

" " available as fuel 7 

Quantity of water formed by burn- \ .„- 

ing 48 parts hydrogen ) 

Hygroscopic Water 200 

Total quantity of water evaporated 632 

Units of Heat. 

400 grammes of carbon yield 3,232 

7 " " hydrogen " 241 

3,473 

Deduct amount of heat required to convert 632 grammes of 

water into vapor. (See §14.) 339 

Calorific power of air-dried wood 3,134 

From the mechanical equivalent of heat given on page 14, 
and from the data of the above table, we can easily calculate 
the mechanical power developed in ordinary combustion, and 
the student will be surprised to find how great this power is. 
The burning of one kilogramme of charcoal produces an 
amount of heat which is equivalent to 8,080 X 423 = 3,41 7,840 
kilogramme metres ; that is, the moving power which is de- 
veloped by the clashing of the atoms during the combustion 
of this small amount of coal is equal to that which would be 
produced by the fall of a mass of rock weighing 8,080 kilo- 
grammes over a precipice 423 metres high, and, could this 
power be all utilized, it would be adequate to raise the same 
weight to the same height, or to do any other equivalent 
amount of work. The steam-engine is a machine for apply- 
ing this very power to produce mechanical results ; but, unfor- 
tunately, in the best engines we do not utilize much more than 
2^ of the power of the fuel ; and to find a more economical 
means of converting heat into mechanical effect is one of the 
great problems of the present aire. 

62. Calorific Intensity. — The calorific intensity of fuel is to 
be carefully distinguished from its calorific power. By calorific 
poiver is meant, as we have seen, the total quantity of heat 
developed by the combustion of a given amount of fuel. By 
calorific intensity, we mean the maximum temperature de- 
veloped in the process of combustion. Provided the products 
are the same, the total amount of heat produced in any case is 



120 COMBUSTION. 

not materially influenced by the rapidity of the process ; but 
it is evident that the temperature of the burning fuel will de- 
pend, other things being equal, on the rapidity with which the 
heat is developed as compared with the rapidity with which it 
is dissipated through surrounding objects ; and, when the com- 
bination with oxygen is very slow, the heat may be dissipated 
as fast as it is generated, and then the temperature of the 
burning body will not rise above that of the surrounding at- 
mosphere, as is the case in many of the processes of slow com- 
bustion. 

Assuming, however, that all the heat is retained by the 
products of combustion, we can calculate the maximum tem- 
perature which can in any case be produced, provided the 
calorific power of the fuel and the specific heat of the products 
of combustion are known. The calorific intensity is simply 
the temperature to which the heat generated by the burning 
of each portion of the fuel can raise the products of its own 
combustion. Assume that the quantity burnt is one kilo- 
gramme, that the calorific power or number of units of heat 
produced is C, that the weights of the various products of com- 
bustion are W, W, W, &c, and that the spec fie heats of 
these products are S, S', S", &c. Then TVS + TV'S 1 + W"S" 
-j-&c, represents the amount of heat required to raise the tem- 
perature of the whole mass of the products one centigrade de- 
gree (§ 16), — and the maximum temperature, to which these 
products can be raised in the process of combustion, must be 

T = WS+ W'S' + TV'S" ^ 6 -° J 

Problem. Find the calorific intensity of charcoal burnt in pure 
oxygen, and also in air under constant atmospheric pressure. 

Solution. By [54] we easily find that each ki'0£ramme of 
carbon yields, by burning, 3.67 kilogrammes of carbonic anhy- 
dride, which is the sole product of its combustion when burnt 
in pure oxygen. The specific heat of carbonic anhydride 
(Chem. Phys. 235) is 0.2164. The calorific pow^r of charcoal 
is 8,0<S0. By substituting these values in [GO] we get T = 
10,174°. 

When the charcoal burns in air, the 3.67 kilogrammes of 
carbonic anhydride formed by the combustion are mixed with a 



COMBUSTION. 121 

large mass of inert nitrogen, which must be regarded as one of 
the products of the combustion. The weight of this nitrogen is 
easily calculated from the known composition of air by weight 
(§ 59) and from the amount of oxygen consumed in the process. 

23.2 : 76.8 = 2.67 : x; or x = 2.67 X 3.31 = 8.84. 

We have now, besides the values given above, W = 8.84 
and S,' the specific heat of nitrogen, equal to 0.244. Whence 

T = 2,738°. 

Problem. Find the calorific intensity of hydrogen gas burnt 
in oxygen and burnt in air. 

Solution. One kilogramme of hydrogen yields 9 kilogrammes 
of aqueous vapor. The specific heat of aqueous vapor is 0.4805. 
The calorific power of hydrogen is not so great when- the gas 
is burnt under ordinary conditions as that given in the table on 
page 118 ; for in the experiments of Favre and Silbermann the 
vapor formed by the combustion was subsequently condensed 
to water, and gave out its latent heat, while in a burning flame 
of hydrogen no Mich condensation takes place. Hence C = 
34,462 — (537 X 9) = 29,629. We also have W= 9 and 
S= 0. 480. Whence T— 6,853°. 

When hydrogen is burnt in air, the nitrogen, mixed with the 
aqueous vapor, weighs 26.49 kilogrammes and S' is the same 
as in the previous problem. Whence V = 2,746°. 

It appears then from these problems, that, although the 
calorific power of hydrogen is much greater than that of car- 
bon, its calorific intensity is less. But it must be remembered 
that the conditions assumed in these problems are never real- 
ized in practice, for the heat generated by the combustion is 
never wholly retained in the products. The process of com- 
bustion requires a certain time, and during this time a portion 
of the heat escapes. Moreover, more air passes through the 
combustible than is required for perfect comhustion, and many 
of the data which enter into the calculation are uncertain. 
The results, therefore, can only be regarded as approximate. 
The theoretical conditions are most nearly realized in a gas 
flame, and especially in that form of burner known as the 
Bunsen lamp. The temperature of the fbime of this lamp, 
when carefully regulated, is very nearly that which the theory 
would assign. 



122 COMBUSTION. 

63. Point of Ignition. — In order that a combustible body- 
should take fire, and continue burning in the atmosphere, it 
must be heated to a certain temperature, and maintained at 
this temperature. This temperature is called the point of igni- 
tion ; and although it cannot always be accurately measured, 
and is undoubtedly more or less variable under different con- 
ditions, yet, nevertheless, it is tolerably constant for each sub- 
stance. For different substances it differs very greatly. Thus 
phosphorus takes fire below the boiling point of water, sulphur 
at 260°, wood at a low red heat, anthracite coal only at a full 
red heat, while iron requires the highest temperature of a 
forge. If a burning body is cooled below its point of ignition, 
it goes out; and our ordinary combustibles continue burning 
in the air only because the heat evolved by the burning main- 
tains the temperature above the required point. If the tem- 
perature of the combustible is not maintained sufficiently high, 
either because the chemical union is too slow, or because the 
calorific power is too small, then the combustible will not con- 
tinue to burn in the air of itself, although it may burn most 
readily if its temperature is sustained by artificial means. 
Hence many of the metals which will not burn in the air 
burn readily in the flame of a blowpipe, and an iron watch- 
spring burns like a match in an atmosphere of pure oxygen. 
The calorific intensity of all combustibles, when burnt in the 
atmosphere, is, as we have seen, greatly reduced by the pres- 
ence of nitrogen ; and hence it is that, although the burning 
watch-spring is maintained above the point of ignition in pure 
oxygen, it soon falls below this temperature, and goes out 
when ignited in the air. Thus it is that the nitrogen of our 
atmosphere exerts a most important influence on the action of 
the fire element ; and it can easily be seen that, were it not for 
these provisions in the constitution of nature, by which the 
active energies of oxygen are kept within certain limits, no 
combustible material could exist on the surface of the earth. 

64. Calorific Power derived from the Sun. — The great mass 
of the crust of our globe consists of saturated oxygen com- 
pounds, or, in other words, of burnt material* ; and the total 
amount of combustible materials which exists on its surface is, 
comparatively, very small. That which exists naturally consists 
almost entirely of carbon and its compounds, — such as coal, 



COMBUSTION. 123 

naphtha, and wood ; and all these substances are the results of 
vegetable growth, either of the present age or of earlier geo- 
logical epochs. Moreover, whatever subsequent changes the 
material may have undergone, it was all originally prepared 
by the plant from the carbonic acid and water of our atmos- 
phere ; for, in the economy of nature, these products of com- 
bustion have been made the food of the vegetable world. The 
sun's rays, acting on the green leaves of the plant, exert a mys- 
terious power, which decomposes carbonic anhydride, and per- 
haps also water ; and, as the result of this process, oxygen is 
returned to the atmosphere, while carbon and hydrogen are 
stored up in the growing tissues of the plant. The sun thus 
undoes the work of combustion, and parts the atoms which the 
chemical affinities had drawn together. In doing this, the 
sun exerts an enormous power ; and the w r ork which it thus ac- 
complishes is the precise measure of the calorific power of the 
combustible material, which it then prepares. When we wind 
up the weight of a clock, we exert a certain power which reap- 
pears in its subsequent motions ; and so, when the sun's rays 
part these atoms, the great power it exerts is again called into 
action, when in the process of combustion the atoms reunite. 
Moreover, what is true of calorific power is true of all mani- 
festations of power on the surface of the earth. Every form 
of motion is sustained by the running down of some weight 
which the sun has wound up ; and, according to the best theory 
we can form, the sun's power itself is sustained by the gradual 
falling of the whole mass of the solar system towards its com- 
mon centre. However varying in its manifestation, all power 
in its essence is the same, and the total amount of power in the 
universe is constant. 

65. Heat of Chemical Combinations. — The heat of combus- 
tion is only a striking manifestation of a very general principle, 
which holds true in all chemical changes. It would appear 
that whenever, in a chemical reaction, atoms or molecules are 
drawn together by their mutual affinities, a certain amount of 
moving power is developed, which takes the form of heat ; and 
whenever, on the other hand, these same atoms or molecules 
are drawn apart by the action of some superior force, the same 
amount of moving power is expended, and heat disappears. 
Every chemical reaction is a mixed effect of such combina- 



124 COMBUSTION. 

tions and decompositions, and it is simply a complex problem in 
the mechanical theory of heat to determine what must be in 
any case the thermal effect. The numerous facts with 
which we are acquainted in regard to the heat of chemical 
combination generally agree with the mechanical theory ; and, 
where the facts do not appear to conform to it, the discrepancy 
probably arises from our ignorance of the nature of the chem- 
ical change in question. It would be incompatible with our 
design to discuss these facts in this book. It must be sufficient 
to state a few general results, which may be summed up in the 
following propositions: — 

First. The heat absorbed in the decomposition of a com- 
pound is equal to the heat evolved in its formation, provided 
the initial and the final states are the same. 

Second. The heat evolved in a series of successive chemical 
changes is equal to the sum of the quantities which would be 
evolved in each separately, provided the bodies are finally 
brought into identical conditions. 

Third. The difference between the quantities of heat evolved 
in two series of changes starting from two different states, but 
ending in the same final state, is equal to that which is evolved 
or absorbed in passing from one initial condition to the other. 

For example, if a body m evolves a certain amount of heat 
in uniting with n to form m n, and if the body m n is decom- 
posed by a third body p, so that m p is formed, the quantity 
of heat evolved in this last reaction is less than that which 
would be evolved in the direct union of m and p by the amount 
evolved in the formation of m n. 

All these propositions, however, are but special cases under 
a more general principle which is at the basis of the whole 
mechanical theory of heat, and which may be enunciated as 
follows : Whenever a system of bodies undergoes chemical 
or physical changes, and passes into another condition, what- 
ever may have been the nature or succession of the changes, 
the quantity of heat evolved or absorbed depends solely on the 
initial and final conditions of the system, provided no mechan- 
ical effect has been produced on bodies outside. 



COMBUSTION. 125 

Questions and Problems. 

1. How many times more space does the carbonic anhydride 
formed by burning charcoal (Sp. Gr. = 2) occupy than the char- 
coal burnt ? 

Ans. One cubic centimetre or two grammes of charcoal yields 
3.720 litres. Hence the gas occupies 3,720 times the volume 
of the charcoal. 

2. How many litres of oxygen gas are required to burn one litre 
of alcohol vapor, and how many litres of aqueous vapor, and how 
many of carbonic anhydride, will be formed in the process ? 

Ans. 3 litres of oxygen, 3 litres of aqueous vapor, 2 litres of car- 
bonic anhydride. 

3. Given the symbol of alcohol C 2 H 6 to find its calorific power. 
Ans. 6,5 72 units, or 7,200 units, assuming that the steam lbrmed 

was condensed. 

4. The composition of dried peat is as follows : Carbon, 625.4 ; 
Hydrogen, 68.1 ; Oxygen, 292.4 ; Nitrogen, 14.1. Find the calor- 
ific power. Ans. 5,521 units. 

5. Find the calorific intensity of marsh gas burnt in oxygen. 

CB 4 -{-2 0=0= C0 2 + 2H 2 

Calorific power of marsh gas, 13,063. Specific heat of steam, 4805 ; 
of C0 2 , 0.2164. Ans. 7,793. 

6. Find the calorific intensity of defiant gas burnt in oxygen. 

C 2 ff 4 + 30 O = 2C0 2 + 2E 2 

Calorific power of C 2 Z7 4 11,858. Specific heat of steam and car- 
bonic anhydride as in last problem. Ans. 9,136°. 

7. Find the calorific intensity of marsh gas and olefiant gas burnt 
in air. Besides the data already given, we have also specific heat of 
nitrogen 0.244. Ans. 2,662°, and 2,916°. 



X 



CHAPTER XIII. 

MOLECULAR WEIGHT AND CONSTITUTION. 



66. Determination of Molecular Weights. — It has already 
been stated that the molecular weight of a substance is an 
essential element in fixing its symbol and in judging of its 
chemical relations, but until now the student has not possessed 
the knowledge necessary in order to understand the methods 
by which this important constant is determined. 

Whenever the substance is a gas, or is capable of being vola- 
tilized without decomposition at a manageable temperature, we 
always ascertain the molecular weight from the specific gravity 
on the principle already several times enforced (§ 17). The 
problem then resolves itself into finding the specific gravity of 
the substance in the state of gas. The methods used in such 
cases are described on page 21, and more in detail in the au- 
thor's work on Chemical Physics (330 et seq.), and in the same 
book tables are given which very greatly facilitate the calcula- 
tion of the results. The specific gravity of the gas or vapor 
having been found by either of these methods, and referred to 
hydrogen gas as the unit, the molecular weight of the substance 
is simply twice the number thus determined. But in applying 
this important principle, on which our modern chemical philoso- 
phy so greatly rests, two precautions are essential. 

It is only true that equal volumes of all substances contain 
the same number of molecules when they are in the condition 
of true gases. Now, while some substances, like alcohol, assume 
this condition at temperatures only a few degrees above their 
boiling point, at least nearly enough for all practical pur- 
poses, others, like acetic acid, only attain it at temperatures one 
or two hundred degrees above their boiling point, and others 
still, like sulphur, only at the very highest temperatures at 
which we have been able to experiment. For this reason, the 
specific gravity of sulphur vapor was for a long time an anomalous 
fact in the science, and it was not until St. Clair Deville, by 



MOLECULAR WEIGHT AND CONSTITUTION. 127 

using a porcelain globe, succeeded in determining its specific 
gravity at a very high temperature, that its value was found to 
correspond with the probable molecular weight, and it is pos- 
sible that a similar anomaly which still exists in the case of 
phosphorus and arsenic may be due to the same cause. 

The chemist, however, can always have a sure criterion of 
the condition of any vapor whose specific gravity he is deter- 
mining by repeating his experiment at a somewhat higher tem- 
perature. If the second result does not agree with the first, it 
is a proof that the vapor is not yet in a proper condition, and 
that the temperature employed in the experiment was too low. 
A series of determinations of the specific gravity of the vapor 
of acetic acid made by Cahours furnish an excellent illustra- 
tion of the importance of the precaution we are discussing, and 
will also point out another important relation of this whole sub- 
ject. This acid when in the most concentrated state boils at 
120°, and the specific gravity of its vapor referred to hydrogen 
at the same temperature and pressure was found to have the 
following values at the temperatures annexed : — 



At 125 


45.90 


At 170 


35.30 


At 240 


30.16 


" 130 


44.82 


" 180 


35.19 


" 270 


30.14 


" 140 


41.96 


" 190 


34.33 


" 310 


30.10 


" 150 


39.37 


" 200 


32.44 


" 320 


30.07 


" 1G0 


37.59 


" 220 


30.77 


« 336 


30.07 



It will be noticed that, as the temperature increases, the 
specific gravity diminishes, at first very rapidly, afterwards 
more slowly, and does not become constant until the tempera- 
ture has risen 200° above the boiling point, when we have the 
true specific gravity of acetic acid in the state of gas. This 
gives for the molecular weight of acetic acid 60 very nearly, 
which corresponds to the received formula, CM±0. 2 . The slight 
difference between the theoretical and the observed results 
may be in part due to errors of observation, but is most prob- 
ably to be referred to the same cause which determines even 
in the permanent gases, when under the atmospheric pressure, 
a variation from Mariotte's law. We do not expect., moreover, 
to find from the specific gravity the exact molecular weight. 
The precise value is determined by the resrdts of analysis, which 
are, as a rule, far more accurate, and the specific gravity is 



128 



MOLECULAR WEIGHT AND CONSTITUTION. 



only used to decide which of several possible multiples must be 
the true value. (Compare carefully § 23.) 

67. Disassociation. — But, besides taking care that the tem- 
perature is sufficiently high to biing the substance we are 
studying into the condition of a true gas, we must look out that 
the compound is not decomposed in the process. It is now well 
known that at very high temperatures the disassociation of 
the elements of a compound body is a constant result, and it is 
probable that in some cases the same effect is produced at the 
much lower temperatures which are employed in the determi- 
nation of vapor densities. The specific gravity of the vapor 
of amnionic chloride, instead of being 2G.75, as we should ex- 
pect from the undoubted weight of its molecule, NH A Cl, is 
only about one half of this amount ; and the reason probably is, 
that, when heated, the molecule breaks into two, and in conse- 
quence the volume of the vapor doubles. 



NHtCl 


= 


NB, 


+ 


HGl 



It is very difficult, however, to obtain any further evidence 
that such a change has taken place ; for, as soon as the tempera- 
ture falls, the molecules recombine in assuming the solid condi- 
tion, and all the phenomena attending the change of state are 
precisely the same as those observed in any other volatile 
body. Indeed, although many very ingenious experiments 
have been made with a view of settling the question, it is still 
uncertain, not only in this, but also in several other cases, 
whether disassociation has taken place or not. The question 
is of great importance to the theory of chemistry. If disasso- 
ciation does not take place, the cases referred to are exceptions 
to the law of equal molecular volumes, and specific gravity can 
no longer be regarded, as now, the sole measure of molecular 
weight. If, however, it can be proved that such a change does 
take place, then the unity of our present theory is preserved,, 
and the chemist has only to guard against this cause of error 
in his experiments. 

68. Indirect Determination of Molecular Weight. — Al- 
though our modern chemical theories rest in great measure on 
the molecular weight of a few typical compounds determined, 



MOLECULAR WEIGHT AND CONSTITUTION. 129 

at least approximately, by their specific gravities, yet it is only 
in a comparatively few cases that we are able to refer the 
molecular weight of a substance directty to this fundamental 
measure. Most substances are so fixed, or so easily decom- 
posed by heat, that it is impossible to determine the specific 
gravity of their vapor, even when such a condition is possible. 
In these cases, however, we endeavor to refer the molec- 
ular weight indirectly to the fundamental measure, by estab- 
lishing a relation of chemical equivalency between the sub- 
stance whose molecular weight is sought and some closely 
allied volatile substance whose molecular weight has been pre- 
viously determined in the manner described above. A few ex- 
amples will make the application of this principle intelligible. 

It is required to determine the molecular weight of nitric 
acid. A careful study of the numerous nitrates leads to the 
conclusion that this acid, like hydrochloric acid, IICl, con- 
tains but one atom of replaceable hydrogen. For example, we 
find but one potassic nitrate and one sodic nitrate, whereas we 
should expect to find several, if the acid were poly basic. 
Hence we conclude that one molecule of argentic nitrate, like 
one molecule of argentic chloride, AgCl, contains but one 
atom of silver. Next, we analyze argentic nitrate, and find 
that 100 parts of the salt contain 63.53 parts of silver. We 
know the atomic weight of silver, 108, and evidently this must 
bear the same relation to the molecular weight of argentic 
nitrate that 63.53 bears to 100. But G3.53 : 100 = 108 : 
a:=rl70, which is the molecular weight of argentic nitrate, 
and, since the molecule of nitric acid differs from that of argen- 
tic nitrate only in containing an atom of hydrogen in place of 
the atom of silver, its own weight must be 170 — 108 -\- 1 
= 63. 

It is required to determine the molecular weight of sul- 
phuric acid. A comparison of the different sulphates shows 
that sulphuric acid is dibasic. We find two sulphates of potas- 
sium and sodium, an acid sulphate and a neutral sulphate, and 
hence we conclude that this acid contains two replaceable 
atoms of hydrogen, and hence that one molecule of neutral 
potassic sulphate contains two atoms of potassium. In ana- 
lyzing potassic sulphate it appears that 10O parts of the salt 
contain 44.83 parts of potassium, and evidently this weight 
9 



130 MOLECULAR WEIGHT AND CONSTITUTION. 

bears the same relation to 100 that the weight of two atoms of 
potassium bears to the weight of the molecule of potassic sul- 
phate. Thus we have, — 

44.83 : 100 =± 78 : x = 174 ; the 31. W. of Potassic Sulphate, 
and 174 — 78 -f 2 = 98 ; the M If. of Sulphuric Acid. 

By a similar course of reasoning we may deduce from the 
results of analysis, and from the general chemical rela- 
tions, the molecular weight of any other acid or base. If 
there is any question in regard to the basicity of the acid or 
the acidify of the base, there will be the same question as to 
the molecular weight ; but we cannot be led far into error, for 
the true weight will be some simple multiple or submultiple of 
the one assumed, and the progress of science will sooner or 
later correct our mistake. From the molecular weight of any 
acid we easily deduce the molecular weights of all its salts. 

When the substance is not distinctively an acid or abase, but 
is capable of entering into combination with other bodies, we 
can frequently discover its molecular weight by determining 
experimental!}' how much of this substance is equivalent to a 
known weight of some allied but volatile substance whose 
molecular weight is known. Thus ammonia gas, whose molec- 
ular weight is one of the best-established data of chemistry, 
enters into direct union with a compound of platinic chloride 
and hydrochloric acid (PtC/ G H.>) to form a definite crystalline 
salt whose composition is exactly known. 

PtClJl 2 -\-2NH,z=z PtCk(NH,). 2 . [Gl] 

Now a very large number of substances allied to ammonia 
form with this same platinum salt equally definite products, so 
that by simply determining the weight of platinum in these 
compounds, which is very easily done, their molecular weights 
may at once be referred to the molecular weight of ammonia. 

Lastly, if other means fail, we may sometimes discover the 
molecular weight of a compound by carefully studying the reac- 
tions by which it is formed or decomposed, and inferring the 
weight of the compound from that of its factors or products. We 
seek to express the reaction in the simplest possible way, and 
give that value to the molecular weight which best satisfies the 



MOLECULAR WEIGHT AND CONSTITUTION. 131 

chemical equation. Evidently, however, such results are less 
trustworthy than those obtained by either of the other methods. 

GO. Constitution of Molecules. — It is a favorite theory with 
some chemists that no molecule can exist in a free condition 
with any of its affinities unsatisfied, but those who hold this 
view are compelled to admit that two points of attraction in 
the same atom may, in certain cases, neutralize each other. 
Hence, they would distinguish between a dyad atom like that 
of oxygen Q ^), with its affinities open, and a dyad atom like 
that of mercury (~jj' w ^ n * ts affinities closed through their own 
mutual attraction. The first could not exist in a free condition, 
while the last could. In like manner any atom, having an even 
number of points of attraction, can exist in a free state because 
all its affinities may be satisfied within itself; but an atom hav- 
ing an uneven number of points cannot, for at least one of its 
affinities must be open as is shown by the symbol ^ — r • ). As 
thus interpreted it must be admitted that the theory explains 
many facts. 

For example, among the univalent elements, chlorine, bro- 
mine and iodine are all known to have molecules consisting of 
two atoms. So, also, the molecule of cyanogen gas consists of 
two atoms of the radical CN, and the same is true of ethyl, 
propyl, &c, at least if the hydrocarbons so named have really 
the constitution first assigned to them. 

Passing next to the dyads, we find that, while oxygen, sulphur, 
selenium and tellurium have molecules consisting of two atoms, 
the metals mercury and cadmium, and the radicals ethylene, 
propylene, &c. (C 2 /^aud C^H^), have molecules which coincide 
with their atoms. 

Of the well-defined triad elements none are volatile, but the 
two triad radicals which have been obtained in a free state- — 
allyl 1 (C s ff 5 ) and kakodyl ((CH 3 ).,As) — both have double 
atomic molecules. 

In like manner none of the tetrad elements are volatile, 
and the only tetrad radicals known in a free state have single 
atomic molecules. 

Of the pentad elements nitrogen has a molecule of two 
atoms, while phosphorus and arsenic have molecules of four 

1 See page 78, Problem 7. 



132 MOLECULAR WEIGHT AND CONSTITUTION. 

atoms. No compound radicals of this order are known in a 
free state. 

Lastly, the only hexad radical known in a free state, benzine, 
CqHq, has a molecule which coincides with its atom. 

Thus it appears that in general the theory is sustained by the 

facts. Nevertheless, there are several well-marked exceptions 

in i 

to it. Thus the well-known compounds NO and N0. 2 have 

molecules which act as radicals of uneven atomicities and yet 
contain but one complex atom. We must be careful, therefore, 
not to give too much weight to this hypothesis, but still it may 
be useful in co-ordinating facts. It leads at once to three gen- 
eral principles which will be found to be almost universally 
true. 

The first is that the sum of the atomicities of the atoms of 
every molecule is an even number. 

The second is that the atomicity of any radical is an odd 
or even number according as the sum of the atomicities of 
its elementary atoms is odd or even. 

The third is that the qnanti valence of elementary atoms 
must be, as stated on page 59, either even or odd. They are 
artiads or perissads, and the two characters can never be mani- 
fested by the same elements. 

It has also been a question among chemists whether molec- 
ular combination was possible ; in other words, whether it is 
possible for molecules of different kinds to combine chemically, 
each preserving its integrity in the compound. Some of the 
advocates of the unitary theory, in the reaction against the 
dualistic system, have been inclined to doubt the possibility of 
such compounds, and have attempted to represent the symbols 
of oil compounds in a single molecular group ; but any ante- 
cedent improbability, on theoretical grounds, is far more than 
outweighed by the evidence of a large number of compounds 
whose constitution is most simply explained on the hypothesis 
of molecular combination. For example, in the crystalline salts 
it is impossible to doubt that the water exists as such, not as a 
part of the salt molecule, but combined with it as a whole. So, 
also, there are a number of double salts whose constitution is 
most simply explained on a similar hypothesis, and, in the pres- 
ent state of the science, it seems unnecessary to complicate 
their symbols by forcing them into the unitary mould. It is a 



MOLECULAR WEIGHT AND CONSTITUTION. 133 

characteristic of such molecular compounds as are here assumed, 
that the force which holds together the molecules is much feebler 
than that which binds together the atoms in the molecule. When 
the molecular attraction is very strong, it is probable that in 
almost all cases the different molecules coalesce into one ; and 
between the extreme limits we find compounds in which it i3 
difficult to determine whether true molecular combination ex- 
ists or not. Such coalescing of distinct molecules seems always, 
however, to be attended with a greater development of heat, and, 
in general, with a more marked manifestation of physical ener- 
gies, than usually attends either molecular aggregation or atomic 
metathesis. 

In the notation of this book molecular combination is indi- 
cated by writing together the symbols of the different molecules 
thus united, but separating these symbols by periods. Thus 
the symbols AKCl.PtC/^ and 3NaF.SbF 3 represent compounds 
of this class. 

70. Isomerism, Allotropism, Polymorphism. — We should 
infer from the doctrine of chemical t} r pes that the same atoms 
might be grouped together in different ways, so as to form 
different molecules which in their aggregation would present 
essentially distinct qualities. Hence, we should expect to find 
distinct substances having the same composition ; and in fact 
our science, organic chemistry especially, is rich in examples 
of this kind. Such substances are said to be isomeric, and the 
phenomenon is called isomerism. There are different phases 
of isomerism, which it will be well to distinguish, not so much 
on account of any essential differences in the phenomena as in 
order to make ourselves better acquainted with its manifesta- 
tions. 

In the first place, we have examples of isomeric bodies 
having the same centesimal composition, but showing no rela- 
tion to each other in their properties or in their chemical 
reactions. Sometimes we have assigned to them the same 
formula, but in other cases the symbol of one is a simple 
multiple of that of the other. Thus aldehyde and oxide of 
ethylene have both the symbol C>H±0\ cane sugar and gum 
arabic, the common formula C vl H tl O n \ lactic acid, the formula 
C z HqO z ; and glucose, C^H v ,0 6 . These compounds bear no 
resemblance to each other, and have no relations in common 



134 MOLECULAR WEIGHT AND CONSTITUTION. 

save the single fact lhat their centesimal composition is the 
same. 

In the second place, we have numerous examples of isomeric 
compounds, which, with the same centesimal composition, have 
also ihe same molecular weight, and whose molecules, therefore, 
consist of the same number of -atoms, but where a fundamental 
difference in the grouping of the atoms may be inferred from 
the nature and products of the chemical reactions, by which such 
isomeric compounds are formed or decomposed. Thus, for ex- 
ample, ethylic formiate (C. 2 II 5 )-0-(CirO) lias exactly the same 
composition and molecular weight as methylic acetate (CH S )' 
0\C 2 H 3 0). The same is true of cyanic ether and cyanetholine, 
whose symbols have already been given (page 77) in connec- 
tion with the reactions, which indicate their molecular constitu- 
tion, and another still more remarkable case will be found in 
Part II. of this work [164] and [165]. 

In the third place, we have several groups of isomeric com- 
pounds, especially among the hydrocarbons, which have the 
same general properties and the same percentage composition, 
but which differ from each other in their molecular weights ; so 
that the symbol of one is a multiple of that of the rest. The 
hydrocarbons ethylene C 2 If 4 , propylene C s ff Q , butylene C 4 ff 8 , 
form a group of this kind. Compounds of this class are fre- 
quently called polymeric, and sometimes the heavier com- 
pounds may be regarded as condensed forms of the lighter. 

Lastly, we may distinguish still a fourth class of isomeric 
compounds which have the same general properties, the same 
symbol, and the same general system of reactions, but which 
differ in a few marked qualities, physical or chemical, and 
which preserve these characteristics to a greater or less extent in 
their compounds. The two forms of toluic acid, C 8 i7 8 2 , be- 
long to this class, and such compounds are isomeric in the 
fullest sense of the word. 

/ In all the above examples the differences between the iso- 
meric compounds are sufficiently great to lead chemists to 
assign to each a distinct name. When, however, the differ- 
ences are not sufficiently great to justify a distinct name, the 
two bodies are said to be different allotropic states of the same 
substance. Thus there are two varieties of tartaric acid ; the 
first of which deviates the plane of polarization of a ray of light 



MOLECULAR WEIGHT AND CONSTITUTION. 135 

to the left, while the second deviates it to the right; but since 
in almost every other respect these two bodies are identical, 
we do not speak of them as different substances, but merely as 
different allotropic states of tartaric acid. There are also three 
other varieties of tartaric acid, but these differ so greatly from 
the normal acid in crystalline form, in solubility, and also in 
other relations, that they may fairly be regarded as distinct 
substances. 

Again, there are many substances where the difference of 
state or ullotropism is associated with difference of crystalline 
form ; and when this difference of form is fundamental, the 
substance is said to be dimorphous or trimorphous, as the case 
may be, and the phenomenon is called polymorphism. Thus 
common calcic carbonate crystallizes in two fundamentally dis- 
tinct forms, corresponding to the two mineral ogical species, 
calcite and aragonite. Such difference of form, however, is 
invariably accompanied by a marked difference of properties, 
so that polymorphism is merely one of the indications of allo- 
tropism. 

Differences of condition similar to those we have described 
manifest themselves even more markedly among elementary 
substances; and indeed the word allotropism was first applied 
to phenomena of this last class. Thus there are two allotropic 
states of phosphorus, which differ so much from each other that 
no one would suspect from their external characters that there 
was any identity between them, and to these two states corre- 
spond two fundamentally different crystalline forms. In some 
cases the differences between the allotropic states of the same 
element are far greater than any which are seen between the 
most unlike isomeric compounds. No substances could be 
better denned by well-marked and utterly distinct qualities 
than diamond, plumbago, and charcoal, and yet they are all 
three allotropic modifications of the one elemental substance 
we call carbon ; and such phenomena as these give us strong 
grounds for believing^ that our present elements may have a 
composite structure. v\ / 

AC 




136 MOLECULAR WEIGHTS AND CONSTITUTION. 



Questions and Problems. 

1. What are the molecular weights of alcohol and camphor as de- 
duced from the results of the £m ($$x. determinations given on page 
23? 

Ans. 45.5 and 155, which, although not closely agreeing with the 
theoretical numbers, enables us to decide that the symbols 
of these compounds are C 2 H Q and C l0 Z7 16 O as the simplest 
interpretation of the analyses would indicate. 

2. At the temperature of 470° the £jn (£$£. of the vapor of sul- 
phuric acid is approximately 1.697. How does this result agree with 
the generally received symbol of this compound, and how do you 
explain the discrepancy ? 

3. A study of the different tartrates has led to the conclusion 
already expressed that tartaric acid, although tetratomic, is dibasic. 
It also appears that one hundred parts of neutral argentic tartrate 
yield when ignited 55.39 parts of metallic silver. Required the 
molecular weight of tartaric acid. Ans. 176. 

4. An hundred parts of baric oxide, BaO, (whose composition is 
assumed to be known) yield when treated with sulphuric acid 152.3 
parts of baric sulphate. Further it is assumed, as the result of care- 
ful study, that sulphuric acid is dibasic, and the metal barium a biva- 
lent radical. " Required the molecular weight of sulphuric acid. 

Ans. 98. 

5. The well-known base aniline gives with platinic chloride a 
definite crystalline product, one hundred parts of which yield on 
ignition 32.99 parts of platinum. Required the molecular weight of 
aniline. How does this result agree with the gp. (*$r. of aniline 
vapor, which has been found by observation to be 3.210. ? 

Ans. 93; which corresponds to Sj). (5r. 0I> 3.223. 

6. The base triethylamine gives in like manner a platinum salt, 
one hundred parts of which yield on ignition 33.67 parts of plati- 
num. Required the molecular weight. Ans. 101. 

7. Compare together the symbols of the compounds of the va- 
rious alcohol radicals on pages 90 to 93 and point out the exam- 
ples of isomerism. 




CHAPTER XIV. 

CRYSTALLINE FORMS. 

71. Relations to Chemistry. — Almost every substance 
affects a definite polyhedral form, although it may manifest 
this tendency only under favorable conditions. Such forms are 
called crystals, and the process of crystalline growth, or de- 
velopment, is called crystallization. The one essential condi- 
tion of crystallization is a certain freedom of motion, and crys- 
tals, more or less perfect, are usually formed whenever a molten 
liquid " sets," or a solid is deposited from a condition of solution 
or of vapor ; and in each case the slower the process the larger 
and the more perfect are the crystals. The crystalline condi- 
tion is, in fact, the normal state of solid matter. It is true that 
there are a few substances which, like glue, are only known in 
the colloid state; but in most of the so-called colloid sub- 
stances this state is abnormal, and there is a constant tendency 
to crystallization. Moreover, its peculiar crystalline form is one 
of the most characteristic, and apparently one of the most es- 
sential, properties of a substance, and is therefore of great value 
in determining its chemical affinities. The study of the geomet- 
rical relations of these forms is, however, in itself a separate 
science, and in this connection we can only dwell on the few 
elementary principles of the subject on which our system of 
chemical classification in part rests. 

72. Definitions. — In the forms of crystals the idea of sym- 
metry is the great controlling principle. Each sub.-tance fol- 
lows a certain law of symmetry, which seems to be inherent, 
anil a part of its very nature; and when, from any cause, the 
character of the symmetry changes, the. substance loses its 
identity, and, even if its chemical composition remains the 
same, it becomes, to all intents and purposes, a different sub- 
stance. In every crystal the symmetry points to a few direc- 
tions, to which not only the position of the planes, but also the 
physical properties of the body, are closely related. Certain of 






138 



CRYSTALLINE FORMS. 



these directions, more or less arbitrarily chosen, are called the 
axes of the crystals, and a crystalline form may be defined as 
a group of similar planes symmetrically disposed around these 
axes. As is evident from this definition a 
crystalline form, like a geometrical form, is 
a pure abstraction, and this conception is 
carefully to be kept distinct from the idea 
of a crystal, which implies not only a cer- 
tain form, but also a certain structure. 
Moreover, in by far the larger number of 
cases the same crystal is bounded by several 
forms. Thus, in Fig. 4, which represents a 
crystal of common quartz, the planes of the 
prism and the planes of the pyramid are 
distinct crystalline forms. 

73. Systems of Crystals. — A careful study of the forms of 
crystals has shown that these forms may be classified under six 
crystalline systems, each of which is distinguished by a peculiar 
plan of symmetry. These division^, it is true, are in a meas- 
ure arbitrary ; for here, as elsewhere in nature, no sharp dividing 
lines are found ; but nevertheless the distinctions on which the 
classification rests are clearly marked. We can only give in 
this book a very imperfect idea of these several plans of sym- 
metry by representing with figures a few of the more charac- 
teristic forms of each. 

74. First or Isometric System. 1 — The three most frequently 
occurring forms of this system are the regular octahedron, the 




Fig. 5. 





Fig. 7. 




rhombic dodecahedron and the cube, Figs. 5, 6, and 7. These 
and all the other forms of the system may be regarded as 



1 Called also monometric. 



CRYSTALLINE FORMS. 



139 



grouped around three equal and similar axes at right angles to 
each other, and hence the name isometric (equal dimensions). 
They present the same symmetry on all sides, and the appear- 
ance of the form is identical, whichever axis is placed in a ver- 
tical position. In this system no variation in the relative posi- 
tions or lengths of the axes is possible, for this would change 
the plan of symmetry on which the system is based. 

7o. Second or Tetragonal System. 1 — The plan of symmetry 
in this system is best illustrated by the square octahedron, Fig. 
8. Of this form the basal section, Fig. 9, is a square, and to 

Fig. 9. 
Fig. 8. Bfl^nRHR Fi S- 10- 




this fact the name of the system refers. The vertical section, 
on the other hand, is a rhomb, Fig 10. Here, as in the first 
system, the forms may all be referred to three rectangular axes, 
but only two have the same length ; the third may be either 
longer or shorter than the others. The last is the dominant 
axis of the form, and hence we always place it in a vertical 
position and call it the vertical axis. The length of the verti- 
cal axis bears a constant ratio to that of the lateral axes in all 
crystals of the same substance, but this ratio differs very greatly 
for different substances, and is therefore an important erystal- 
lographic character. The familiar square prism is another very 
characteristic form of this system. 

Fig. 11. Fig. 12. 





Moreover, the planes both of the prism and of the octahedron 
may have different positions with reference to the lateral axes, 
as is shown by the two basal sections, Figs. 11 and 12; 

1 Ciillcd also dimetric. 



140 



CRYSTALLINE FORMS. 



and this leads us to distinguish two square prisms and two 
square octahedrons, one of which is said to be the inverse of 
the other. 

76. Third or Hexagonal System. — In the last system the 
planes were arranged by fours around one dominant axis, while 
in this system they are arranged by sixes. The most character- 
istic forms of this system are the hexagonal pyramid, Fig. 13, 
and the hexagonal prism, Fig. 14. The basal section through 
either of these forms is a regular hexagon, Fig. 15, and, besides 

Fig. 13. 

Fig. 14. Fig. 15. 






the dominant or vertical axis, we also distinguish as lateral axes 
the three diagonals of this hexagonal section. These lateral 
axes stand at right angles to the vertical axis, but between 
themselves they subtend angles of 60°, Here, as before, the 
ratio of the length of the vertical axis to the common length of 
the lateral axes has a constant value on crystals of the same 
substance, but differs very greatly with different substances, 
the vertical axis being sometimes longer and sometimes shorter 

Fig. 17. 





than the other three. The rhombohedron, Fig. 16, and the 
scalenohedron, Fig. 17, are also forms of this system, and occur 



CRYSTALLINE FORMS. 



141 



even more frequently than the more typical forms first men- 
tioned. Lastly, a difference of position in the planes of the 
prism or pyramid with reference to the lateral axes gives rise 
in this system to the same distinction between the direct and 
the inverse forms as in the last. 

77. Fourth or Orthorhombic System. 1 — The most character- 
istic forms of this system are the rhombic octahedron, Fig. 18, 
and the right rhombic prism, from which the system takes its 
name. The three principal sections of the octahedron, repre- 
sented by Figs. 19, 20, and 21, and also the basal section of the 



Fig. 19 



Fig. 20. 




prism, are all rhombs, whose relations to the form are indicated 
by the lettering of the figures. TVe easily distinguish here three 
axes at right angles to each other, but of unequal lengths, and 
in regard to the ratios of these lengths the remarks of the last 
two sections are strictly applicable. 

78. Fifth or Monoclinic System. — The forms classed together 
under this system may be referred to three unequal axes, one of 
which stands at right angles to the plane of the other two, while 
they are inclined to each other at an angle, which, though con- 
stant on crystals of the same substance, varies very greatly with 
different substances, as vary also the relative dimensions of the 
axes themselves. Fig. 22 represents an octahedron of this 
system, and Figs. 23 and 24 represent two sections made 
through the edges FF and DD' of this form. A section 
through the edges CO would be similar to Fig. 23, and these 
three sections give a clear idea of the relative positions of the 
axes. The section, Fig. 24, containing the two oblique axes, 

1 Called also trimetric. 



142 CRYSTALLINE FORMS. 

is called the plane of symmetry, and the faces on all mbnoclinic 
crystals are disposed symmetrically solely with reference to this 
plane. In a word, the symmetry is bilateral, and corresponds 

Fig. 22. Fig. 23. Fig. 24. 




to the type with which we are so familiar in the structure of 
the human body. This plan of symmetry is well illustrated by 
Figs. 25, 26, and 27, which represent the commonly occurring 
forms of gypsum, augite, and felspar, three of the most com- 
mon minerals. These figures, however, do not, like those of the 
previous sections, represent simple crystalline forms. The crys- 
tals here represented are in each case bounded by several forms, 
and indeed in this system such compound forms are alone pos- 
sible, for no simple monoclinic form can of itself enclose space. 

Fig. 25. Fig. 26. Fig. 27. 






79. Sixth or Triclinic System. — This system is distinguished 
by an almost complete want of symmetry. Only opposite planes 
Fig. 28. are similar, and two such planes constitute a 

complete crystalline form. Hence on every 
crystal there must be at least three simple forms. 
We may refer the planes of any crystal to 
three unequal axes all oblique to each other, 
but the position we assign to them is quite ar- 
bitrary, and they have therefore little value as 
crystallographic elements. Fig. 28 represents 
a crystal of sulphate of copper, one of the very few subtances 
which crvstallize in this system. 




CRYSTALLINE FORMS. 



143 



80. Modifications on Crystals. — "When several crystalline 
forms appear on the same crystal, some one is usually more 
prominent or dominant than the rest, and gives to the crystal 
its general aspect, the planes of the secondary forms only ap- 
pearing on its edges or solid angles, which are then said to be 
modified or replaced. Thus, in Figs. 29, 30, and 31, the solid 
angles of a cube are replaced (or truncated) by the faces of an 
octahedron ; in Fig. 32 the edges of the cube are replaced by 
the' faces of the dodecahedron ; in Fig. 33 the edges of the 
octahedron are modified in the same way ; and in Fig. 34 the 
solid angles of a dodecahedron are replaced by the faces of an 



Fig. 29. 



Fig. 30. 



Fig. 31. 




octahedron. These are all forms of the isometric system, and 
the relations of the simple forms to each other, which deter- 
mine in every case the position of the secondary planes, will 
be readily seen on comparing together the figures already 
given on page 138. These figures, like all crystallographic 
drawings, are geometrical projections, and represent the planes 
in the same relative position towards the crystalline axes which 
they have on the crystal itself. Moreover, since in all figures 
of crystals of this system the axes are drawn in absolutely 
the same position on the plane of the paper, the same face has 
also the same position throughout. 

As a general rule, all the similar parts of a crystal are 
simultaneously and similarly modified. This important law, 



144 



CRYSTALLINE FORMS. 



which is a simple inference from the principles already stated, 
is illustrated by the figures just given, and also by Figs. 

Fig. 35. Fig. 36. Fig. 37. Fig. 38. 




similar practice he will learn, better than from any descrip- 
tions, how clearly the modifications on a crystal point out its 
crystallographic relations. 



CRYSTALLINE FORMS. 



145 



81. Hemihedral Forms. — To the law governing the modi- 
fications of crystals just stated, there is one important excep- 



Fig. 45. 



Fig. 46. 



Fig. 47. 



Fig. 48. 






gaH 







tion. It not unfrequently happens that half the similar parts 
of a crystal are modified independently of the other half Thus 



Fig. 49. 




Fig. 50. 




in Fig. 51 only one half of the solid angles of the cube are 
truncated. The modifying form in this case is the tetrahedron, 

Fig. 52. 

Fig. 51. HMffi Fig. 03. 




Fig. 53, also a simple form of the isometric system. "When 
all the solid angles of the cube are truncated, the modifying 
form, as has been shown, is the octahedron, and the relation 
which the tetrahedron bears to the octahedron is shown by 
Fig. 52. The rhombohedron, Fig. 54, stands in a similar re- 
lation to the hexagonal pyramid, Fig. 55. From these figures 



1IG 



CRYSTALLINE FORMS. 



it is evident that while the octahedron and the hexagonal pyra- 
mid have all the planes which perfect symmetry requires, the 



Fig. 54. 



Fig. 55. 





tetrahedron and the rhombohedron have only half the number, 
and in crystallography all forms which bear a similar relation 
to the forms of perfect symmetry are said to be hemihtdr'd\ f 
while the forms of perfect symmetry are distinguished as holo- 
hedral. The hemihedral forms are quite numerous in all the 
systems, but with the exception of the tetrahedron, rhombohe- 
dron, and scalenohedron (Fig. 17), they seldom appear except 
as modifying planes on the edges or solid angles of the more 
perfect forms. As a general rule, they are easily recognized, 
but not unfrequently they give to a crystal the aspect of a dif- 
ferent system from that to which it really belongs, and may 
lead to false inferences ; but these can, in most cases, be cor- 
rected by a careful study of the interfacial angles. 

82. Identity of Crystalline Form. — As has already been 
stated, every substance is marked by certain peculiarities of 
outward form, which are among its most essential qualities, and 
we must next learn in what these peculiarities consist. As a 
general rule, the same substance crystallizes in the same form, 
but under unusual circumstances it frequently appears in other 
forms of the same system. Thus fluorspar is usually found 
crystallized in cubes, but in large collections crystals of this 
mineral may be seen in almost all the holohedral forms of the 
isometric system, including their numerous combinations. In 
like manner common salt usually crystallizes in cubes, but out 
of a solution containing urea it frequently crystallizes in octa- 
hedrons. Moreover, the same principle holds true in regard 
to substances crystallizing in other systems, most of whose 
forms never appear except in combination. Thus the mineral 



<m 



CRYSTALLINE FORMS. 147 

quartz generally shows the simple combination represented in 
Fig. 4 ; but more than one hundred other forms, all, however, 
belonging to the same system, have been observed on crystals 
of this well-known substance. So also the crystals of gypsum, 
augite, and felspar, in most cases present the forms already 
figured on page 142, although other forms are common, which, 
however, in each case all belong to the same crystalline system. 
"VVe never find the same substance in the forms of different sys- 
tems except in those cases of polymorphism already described, 
page 135, where the differences in other properties are so great 
that the bodies can no longer be regarded as the same sub>tance. 

Among substances crystallizing in the isometric system the 
crystalline form is not so distinctive a character as it is in other 
cases. In this system the relative dimensions are invariable, 
and the octahedron, the dodecahedron, and the cube, more or 
less modified by different replacements, are the constantly re- 
curring forms. Even here, however, specific differences may 
at times be found in the fact that some substances affect hemi- 
hedral forms on modification, while others do not. In all the 
other systems the dimensions of the crystal (the relative lengths 
of its axes and the values of the interaxial angles) distinguish 
each substance from every other. But here, also, the general 
statement must be somewhat modified. 

We frequently find on the crystals of the same substance 
several forms having different axial dimensions. Thus, on the 
crystal represented by Fig. 56, belonging to the tetragonal 
system, there are three different octahedrons, and three cor- 
responding values of the vertical axis. But if, beginning with 
the planes of the octahedron 0, we determine 
the ratio which its vertical axis bears to the Flg ' 56 ' 

common length of the two lateral axes, and 
call this value a, we shall find that the cor- 
responding values for the two other octahe- 
drons are 2a and ±a respectively. More- 
over, if we extend our study we shall also 
find that this example illustrates a general 
principle, and that the crystalline forms of 
a given substance include not only those of 
identical axial dimensions, but also those whose dimensions bear 
to each other some simple ratio. 




148 CRYSTALLINE FORMS. 

This most important law gives to the science of crystallog- 
raphy a mathematical basis, and enables us to apply the exhaus- 
tive methods of analytical geometry in discussing the various re- 
lations of the subject. Among the actual forms of a given sub- 
stance we fix on some one as the fundamental form, and, taking 
the values of its axial dimensions as our standards, we are able 
to express the position of the planes of all the possible forms by 
means of very simple symbols, and also to express by mathe- 
matical formulae the relations of the interfacial angles to the 
same fundamental elements of the crystal ; so that the one 
may readily be calculated from the other. 

It may seem at first sight that the crystallographic distinction 
between different substances, insisted on above, is greatly ob- 
scured by the important limitations just made. But it is not 
so, at least to any great extent. The selection of the funda- 
mental form of a given substance is not arbitrary, although it is 
based on considerations which it lies beyond the scope of this 
book to discuss. Moreover, an error in this choice is not fun- 
damental, since the true conception of the form of a substance 
includes not only the fundamental form, but all those which are 
related to it. This conception, though not readily embodied in 
ordinary language, is easily expressed by a general mathemat- 
ical formula, and is as tangible to one familiar with the subject 
as the general statement first made. 

But however obscure, to those who are not familiar with 
mathematical conceptions, may be the distinction between the 
forms of different substances in the same system, the difference 
between the different systems is clear and definite, and it is 
with this broad distinction that we have chiefly to deal in our 
chemical classification. 

83. Irregularities of Crystals. — It must not be supposed 
that natural crystals have the same perfection of form and 
regularity of outline which our figures might seem to indicate. 
In addition to being more or less bruised or broken from acci- 
dental causes, crystals are rarely terminated on all sides, — one 
or more of the faces being obliterated where the crystal is im- 
planted on the rock, or where it is merged in other crystals. 
But by far the most remarkable phase which the irregularities 
of crystals present is that shown by Figs. 57 to 67. By com- 
paring together the figures which have been here grouped to- 



CRYSTALLINE FORMS. 



14a 



gether on the page, and which represent in each case different 
phases of the same crystalline form, it will be seen that the 
variations from the normal type are caused by the undue de- 
Fig. 58. 
Fig- 57. M" III in I ■IIHI II ii MM I llllll III 1 1 in ■■ I mill i Fig. 59. 



^±-^z—^F^ 



velopment of certain planes at the expense of their neighbors, 
or by an abnormal growth of the crystal in some one direction. 

Fig. 61. 










Such forms as these, however, although great departures 
from the ideal geometrical types, are in perfect harmony with 

Fig. 62. 



Fig. 63. 





the principles of crystallography. The axis of a crystal is not 
a definite line, but a definite direction ; and the face of a crystal 



150 



CRYSTALLINE FORMS. 



is not a plane of definite size, but simply an extension in two 
definite directions. These directions are the only fundamental 
elements of a crystalline form, and they are preserved under 

Fig. 66. 



Fig. 64 




all conditions, as is proved by the constancy of the interfacial 
angles, and of the modifications, on crystals of the same sub- 
stance, however irregular may have been the development. 

84. Twin Crystals. — Every crystal appears to grow by the 
slow accretion of material around some nucleus, which is usually 
a molecule or a group of molecules of the same substance, and 
which we may call the crystalline molecule or germ. Now we 
must suppose that these molecules have the same differences on 
different sides which we see in the fully developed crystal, and 
which, for the want of a better term, we may call polarity. As 
a general rule, in the aggregation of the molecules a perfect 
parallelism of all the similar parts is preserved. But, if molec- 
ular polarity at all resembles magnetic polarity, it may well be 
that two crystalline molecules might become attached to each 
other in a reversed position, or in some other definite position 
determined by the action of the polar forces. Assume now that 
each of these crystalline molecules " germinate-," and the result 
would be such twin crystals as we actually find in nature. The 
result is usually the same as if a crystal of the normal form 
were cut in two by a plane having a definite po-ition towards 
the crystalline axes, and one part turned half round on the 
other; and twins of this kind are therefore called hemitropes. 
Figs. G8 to 71. At other times the germinal molecules seem 
to have become attached with their dominant axes at right 
angles to each other, and then there result twins such as are 
represented in Figs. 72 and 73 ; and many other modes of twin- 



CRYSTALLINE FORMS. 



151 



ning are possible. Some substances are much more prone to 
the formation of twin crystals than others, and the same sub- 
stance generally affects the same mode of twinning, which may 

Fig. 71. 
Fig. 68. Fig. 70. 

Fisr. 




thus become an important specific character. The plane which 
separates the two members of a twin crystal, called the plane 

Fig. 72. 

Fig. 73. 





of twinning, has always a definite position, and is in every case 
parallel either to an actual or to a possible face on both of the 
two forms. 

Twin crystals always preserve the same symmetry of group- 
ing, and the values of the interfacial angles between the two 
forms are constant on crystals of the same substance, so that 
they might sometimes be mistaken for simple crystals by un- 
practised observers. There is, however, a simple criterion by 
which they can be generally distinguished. Simple crystals 
never have re-entering angles, aud, whenever these occur, the 
faces which subtend them must belong to two individuals. 

The same principle which leads to the formation of twin 
crystals may determine the grouping of several germinal 
molecules, and lead to the formation of far more complex com- 



152 CRYSTALLINE FORMS. 

binations. Frequently, as it would seem, a large number of 
molecules arrange themselves in a line with their principal 
axes parallel and their dissimilar ends together, and hence re- 
sult linear groups of crystals alternating in position, but so fused 
into each other as to leave no evidence of the composite char- 
acter except the re-entering angles, and frequently these are 
marked only by the striations on the surface of the resulting 
faces. Such a structure is peculiar to certain minerals, and 
the resulting striation frequently serves as an important means 
of distinction. The orthoclase and the klinoclase felspars are 
distinguished in this way. 

85. Crystalline Structure. — The crystalline form of a body 
is only one of the manifestations of its crystalline structure. 
This also appears in various physical properties, which are fre- 
quently of great value in fixing the crystallographic relations 
of a substance, and such is especially the case when, on ac- 
count of the imperfection of the crystals, the crystalline form is 
obscure. Of these physical qualities one of the most impor- 
tant is cleavage. 

As a general rule, crystallized bodies may be split more or 
less readily in certain definite directions, called planes of cleav- 
age, which are always parallel either to an actual or to a pos- 
sible face on the crystals of the substance, and are thus inti- 
mately associated with its crystalline structure. At times the 
cleavage is very easily obtained, when it is said to be eminent, 
as in the case of mica or gypsum, which can readily be split 
into exceedingly thin leaves, while in other cases it can only 
be effected by using some sharp tool and applying considerable 
mechanical force. With a few unimportant exceptions the 
cleavage planes have the same position on all specimens of the 
same substance. Thus specimens of fluor-spar mny be readily 
cleaved parallel to the faces of an octahedron, Fig. 5, those of 
galena parallel to the faces of a cube, Fig. 7. those of blende 
parallel to the faces of a dodecahedron, Fig. 6, and those of 
calc-spar parallel to the faces of a rhombohedron, Fig. 1 6. In 
these cases, and in many others, the cleavage is a more distinc- 
tive character than the external form, and can be more fre- 
quently observed, and we generally regard the form produced 
by the union of the several planes of cleavage as the funda- 
mental form of the substance. 

Again, we always find that cleavage is obtained with equal 



CRYSTALLINE FORMS. 153 

ease or difficult) 7 parallel to similar faces, and with unequal 
ease or difficulty parallel to dissimilar faces. Moreover, the 
dissimilar cleavage faces thus obtained may generally be dis- 
tinguished from each other by differences of lustre, striation, 
and other physical character ; and such distinctions are fre- 
quently a great help in studying the crystallographic relations 
of a substance. Similar differences on the natural faces of 
crystals are also equally valuable guides. 

But, of all the modes of investigating the crystalline structure 
of a body, none can compare in efficiency with the use of polar- 
ized light. It is impossible to explain the theory of this beau- 
tiful application of the principles of optics without extending 
this chapter to a length wholly incompatible with the design of 
this book. It must suffice to say, that if we examine with a 
polarizing microscope a thin slice of any transparent crystal of 
the second or third system, cut perpendicular to the dominant 
axis, we see a series of colored rings, intersected by a black 
cross, and it is evident that the circular form of the rings 
answers to the perfect symmetry which exists in these systems 
around the vertical axis. If, however, we examine in a similar 
way a slice from a crystal of one of the last three systems, cut 
in a definite direction, which depends on the molecular structure, 
and must be found by trial, we see a series of oval rings with 
two distinct centres, indicating that the symmetry is of a dif- 
ferent type. Moreover, the distribution of the colors around 
the two centres corresponds in each ca-e to the peculiarities of 
the molecular structure, and enables us to decide to which of 
the three systems the crystal belongs. 

The use of polarized light has revealed remarkable differ- 
ences of structure in different crystals of the same substance, 
connected with the hemihedral modifications described above. 
The Figures 74 and 76 represent crystals of two varieties of 
tartaric acid, which only differ from each other in the position 
of two hemihedral planes, and are so related that when placed 
before a mirror the image of one will be the exact representa- 
tion of the other. The intermediate Figure, 75, represents the 
same, crystal without these modifications. Since the solid 
angles are all similar, we should expect to find them all modi- 
fied simultaneously ; but, while on crystals of common tartaric 
acid only the two front angles (as the figure is drawn) are re- 
placed, a variety of this acid has been discovered having simi- 



154 



CRYSTALLINE FORMS. 



lar crystals, whose back angles only are modified. Now, it is 
found that a solution of the common acid rotates the plane of 
polarization of a beam of light to the right, while a similar so- 



ng. 74. 



Fig. 75. 



Fig. 76. 




lution of this remarkable variety rotates the plane of polariza- 
tion to the left. This difference of crystalline structure, more- 
over, is associated with certain small differences in the chemi- 
cal qualities of the two bodies ; but the difference is so slight 
that we cannot but regard them as essentially the same sub- 
stance, and the polarized light thus reveals to us the beginnings 
of a difference of structure, which, when more developed, mani- 
fests itself in the phenomena of isomerism. It is a remarkable 
fact, worthy of notice in this connection, that these two varieties 
of tartaric acid chemically combine with each other, forming a 
new substance called racemic acid. 

Questions. 

1. By what peculiar mode of symmetry may each of the six crys- 
talline systems be distinguished ? How may crystals belonging to 
the 1st system be recognized V How may crystals of the 2d, 3d, 
and 4th systems be distinguished by studying the distribution of 
the similar planes around their terminations or dominant axes ? 
By what peculiar distribution of similar planes may the crystals of 
the 5th and 6th systems be distinguished from all others? State 
the system to which each of the crystals, represented by the various 
figures of this chapter, belongs, and give the reason of your answer 
in every ease. 

2. We find in the mineral kingdom two different octahedral forms 
of titanic acid belonging to the tetragonal system. In one of these 
forms the ratio of the unequal axes is 1 : 0.6442, in the other it is 
1 : 1.7723. Can these forms belong to the same mineral srbstanee ? 






CHAPTER XV, 



ELECTRICAL RELATIONS OF THE ATOMS. 



Fiar, 77. 




86. General Principles. — If in a vessel of dilute sulphuric 
acid (one part of acid to twenty of water) we suspend a 
plate of zinc and a plate of platinum, opposite to each other, 
and not in contact, we find that no chemical 
action whatever takes place, provided the 
zinc and the acid are perfectly pure. As 
soon, however, as the two plates are united by 
a copper wire, as represented in Fig. 77, chem- 
ical action immediately ensues, and the follow- 
ing phenomena may be observed. First : 
Bubbles of hydrogen gas are evolved from the 
surface of the platinum plate. Secondly : 
The zinc plate slowly dissolves, the zinc combining with the 
radical of the acid to form zincic sulphate, which is soluble in 
water. Lastly : A peculiar mode of atomic motion called 
electricity is transmitted through the copper wire, as may be 
made evident by appropriate means. If the connection be- 
tween the plates is broken by dividing the conducting wire, 
the chemical action instantly stops, and the current of elec- 
tricity ceases to flow ; but, as soon as the connection is renewed, 
these phenomena again appear. 

Similar effects may be produced by other combinations than 
the one just mentioned, provided only certain conditions are 
realized. In the first place, the two plates must consist of 
materials which are unequally affected by the liquid contained 
in the vessel, or cell ; and the greater the difference in this 
respect, within manageable limits, the better. In the second 
place, the materials, both of plates and connector, must be con- 
ductors of electricity ; and, lastly, the liquid must contain some 
substance for one of whose radicals the material of one of the 
plates has sufficient affinity to determine its decomposition un- 
der the conditions present. Such a combination is called a 



156 ELECTRICAL RELATIONS OF THE ATOMS. 

Voltaic Cell. The mode of action of this instrument, wliich 
since its first discovery has been a subject of controversy, is 
very obscure, but the following theory gives an intelligible ex- 
planation of the general phenomena, and may serve a useful 
purpose until greater certainty can be attained. 

Polarity. The phenomena of magnetism have made ns familiar, with a 
condition of matter we call polarity, in wliich bodies manifest a mode of 
energy known as polar force.. The characteristics of po.ar force are as 
follows : — 

1. The energy is chiefly concentrated at opposite points of the polarized body 
called its poles. 2. The pules differ in kind in so few that, while, unlike poles 
attract, like poks repel each other, and while unlike poles neutralize, like poles 
enhance each the ether s effect. 3. With every pole is always associated its op- 
posite, either on the same or a neighboring body, and in every polar system the 
sum [ of the polar energies of one kind is exactly equal to that of those of the 
opposite kind. 4. A polarized body induces a similar state in a I neighboring 
bodies susceptible of this condition, n pe>le of a given kind determining nearest 
to itself a pole of the opposite kind. 5. Induction is attended with no loss of 
energy in the inducing body, whose condition is frequently exalted by the reaction 
of the induced polarity. G. Polarity appears of different kinds ets wJl as in 
different degrees ; the phenomena of magnetic, electrical, and chemical polarity, 
though similar in their general features, differing widely in th-ir modes of man- 
ifestation. 7. Substances differ from each other, not only in their susceptibility 
to polarity of any given kind, but. also in their power of retaining it. 2 

The study of this class of phenomena lias shown that the energy man- 
ifested by polarized bodies is always the effect of an attraction or repul- 
sion between poles, and ihat whenever they appear to act on a neutral 
body the last is always first polarized by induction. Thus the nails 
attracted by a magnet or the straws attracted by an electrified stick of 
sealing-wax are all in a polar condition. A horseshoe magnet, with 
its keeper attached, affords a familiar illustration of these principles, which 
will aid us in explaining the more obscure phenomena of the Voltaic 
cell. The horseshoe magnet was originally polarized by induction, and 
since it is made of hardened steel retains its magneti-m. The soft-iron 
keeper while in contact wbh the magnet is as truly polariz' d as the steel. 
It has a north pole in contact with the south pole, and a south pole in 
contact with the north pole of the magnet. But the mouvnt it is with- 
drawn, all its polar ty disappears. Again, while the magnetic circuit, as 
we call it, is closed, the keeper, by reacting on the source of power, greatly 
enhances the energy of the magnet, which will lift a much greater weight 
suspended from the keeper than it can when the two noes act separately, 
fig. 77 a . Lastly, if we break a steel 

— -f- magnet each of the pa; its will 

S ffeJ "^ ---^ -^fc^ _/ ^^. ^ ^--^ -^j^ - be found to be ma 1 .- ne i zed with 

_|_ ' aa '"^ J " J 'X "'"' _r— ^ — — '' ° ^— =—-^'^ poles rcl itivelv situated as is 

( s^^ct i v^~^...-~^;.r- ---V shown in Fig. '77 a, and since 
° _ • ^ ° u this relation of parts is pre- 

1 There may be several poles oi the same mass of matter, arc! the polarity 
may b > very irregularly distributed. Such i« frequently the condition of the 
lode-stone or of a s'eel bar irregularly magn^tizM. 

2 For exam le, fh a metals iron, nickel, a ; d cobalt, with a few of their com- 
pounds are the only substances suscent'ble <"f magne ic p^larih to a high 
degree. Again, a. hardened steel bar mains the Dolar cond'ti 'ii more or less 
permanently as in f he common magnet, but soft iron loses its magnetic virtue 
the moment the inducing cause ceases to act. 



ELECTRICAL RELATIONS OF THE ATOMS. 157 

served, however far we may carry the subdivision, we are led to the conclu- 
sion that the polarity is a 

quality inherent, not in the ^_ _ v __ __ _ Ig ' ' -^ _^ _^ _^ 
bar as a whole, but in the (D^CCOOCDOO© 

ss.asrstsr.iL' ©ccccccc©©© 

is rudely represented in Fig. 77 6. 

Theory of Chemical Polarity. As the molecules of iron may he mag- 
netically polarized, we infer that the molecules of all substances are sus- 
ceptible of ditferent polar states, and we conceive that chemism l is a 
manifestation of a molecular condition, which we may distinguish as 
chemical polarity. It must be remembered, however, that we do not un- 
derstand the cause of the differences in the various modes of polar energy; 
and in saving that the molecules of matter may be chemically polarized, 
we mean merely that they are susceptible of a condition wh se general 
features have been indicated above Our theory fuither assumes that 
with some molecules the polarity is inherent and theiefore permanent, 
while with others it can only be induced by extraneous causes. These 
last, however, may become polarized by induction to as high or even a 
higher degree than the first, but the condition, like that of an electro- 
magnet, is transient, varying with the inducing cause. Again, as every 
analogy would lead us to believe, our theory further assumes that different 
substances are susceptible of chemical polarity (whether it be inherent or 
assumed) to very different degrees, and that the susceptibility varies un- 
der different conditions. Lastly, our theory supposes that the chemical 
activity of a substance depends on the degree of polarity in hen nt in its 
molecules, and it refers the well known active qualities of acids and 
alkalies to the 'act that their peculiar constitution renders their molecules 
strongly polarized, while the inert qualities of most of the elementary 
substances is explained by the neutral condition which their homogeneous 
structures would naturally produce in their molecules. Thus, for exam- 
ple, we suppose that every molecule of sulphuric acid, 7/ 2 =6'0 4 , or of hy- 
drochloric acid, 11-Cf, or of sodx hydrate, II-NaO, is naturally polarized, 
while on the other hand the molecules of zinc, Zn, of magnesium, Mr/, 
of hydrogen, H-II, and of oxygen, 0=0, are all normally neutral. As 
soon, however, as we place zinc in contact with dilute sulphuric acid, 
the metallic molecules become polarized by induction to the degree of 
which they are susceptible under the influence of this acid. A powerful 
attraction is thus developed and a familiar chemical change is the result. 
If magnesium is treated in a similar way, the action is more energetic, 
because, as wc suppose, the molecules of this metal are susceptible of a 
higher degree of polarity, and the force developed is therefore proportion- 
ally stronger. On the other hand, with metallic copper there is no action 
under the same conditions, because the molecules of the metal do not ac- 
quire a sufficient degree of polarity to determine chemical change. 

While, however, the molecular structure appears to be the most impor- 
tant, it is evidently by no means the only cause which determines chemical 
polarity. The highly active qualities of the alkaline metals and of the 
chlorine group of elementary substances indicate that their molecules, 
although apparently homogeneous in structure, must be permanently 
polarized. Moreover, the fact that a high degree of energy is developed 
in many of the elementary substances, as in oxygen gas, by a simple ele- 
vation of temperature, and the general principle that heat hastens chem- 

1 This term is synonymous with the old term chemical affinity, to which it 
is on many accounts to be preferred. 



158 ELECTRICAL RELATIONS OF THE ATOMS. 

ical chances, Feera to indicate that the polar condition may be frequently 
produced by this agent alone. So also the process of photography is 
most simply explained by the theory that the sun's rays excite a similar 
condition in the silver compounds on the surface of the sensitive plate, 
and the (ffect of continuous electrical discharges in converting oxygen 
gas into that peculiar active modification of this substance called ozone, 
may be regarded as a direct result of their polarizing power. 

Theory of Electricity. The study of the phenomena of optics has led 
physicists to the conclusion that there exists throughout space, filing not 
only the interplanetary but also the intermolecular spaces, a highly atten- 
uated but at the same time wonderfully elastic medium which is called 
the ether (92). Again, the phenomena of heat indicate thar, thj molec- 
ular forces have an energy which is adequate to cope with this very great 
elasticity ; and we cm conceive that they condense around these molecules 
greater or less quantities of this ether, thus giving to each a distinct at- 
mosphere, but one which merges into that universally diffused medium 
in which molecule and planet alike float. Now our theory supposes that 
electrical phenomena are caused by disturbances in the com o»\ ion of 
these ethereal atmospheres. The electrical ether, 1 as we assume, consists of 
two separable materials, which, adopting names long used in science, we 
will call positive and negative or vitreous and resmous electricities. In 
all the terrestrial region of the solar system at least these electricities are 
blended in certain definite proportions, like he constituents of the earth's 
atmosphere, but by various causes they may become separated and more 
or less isolated either on the same or on different molecules. Whenever 
this takes place, the two electricities tend to flow together until the nor- 
mal condition is restored in accordance with the law of diffusion ; but the 
force of diffusion in these molecular atmospheres is vastly greater and 
the process vastly more rapid than it is in the terrestrial atmosphere, be- 
cause the elasticity of the eth°r so greatly exceeds that of the air. This 
being granted, our theory further supposes that every process of electrical 
excitement causes a separati n of tho constituents of the ether, and that 
an electrified body is one on whose molecules one or the o'her of the two 
electricities is to a greater or less degree isolated ; and again, that the fa- 
miliar phenomena of attraction and repulsion between ele'- r rified bodies are 
the effects of pressure caused by the diffusive force ; and lastly, that an 
electrical current consists in an actual transfer of the ethereal material 
between the molecules of the conductor. We have not space, however, 
to follow out the th ory into its mechanical details, and we must content 
ourselves with applying it to the explanation of the phenomena of the 
Voltaic cell. 

Theory of Voltaic Cell. In studying chemical reactions we have thus 
far overlooked the molecular atmospheres ; but it is evident that, if 
the above theory is correct, they must ent^r as impor ant factors into 
every chemical change. This theory assumes that the condition of the 
atmosph re is intimately connected with that of the molecule, although 
in what way it does not attempt to explain. When the molecule is polar- 
ized, the two electricities are more or less fully separated and isolated 
around the molecular poles ; and if the polarity is inherent this condition 
is permanent If, however, the polar state is induced, the neutral condi- 
tion is restored as soon as the inducing force ceases to act. Let us study 
now from this new point of view the familiar reaction of sulphuric acid 
on zinc referred to above. 

Zia + (H 2 SO, + Aq) = (ZnSOt + Aq) + BO-HI. 

1 As it is not important for our present purpose to inquire whether the elec- 
trical ether is identical or only is mingled with the luminiferous ether, this 
question is here left in abeyance. 



ELECTRICAL RELATIONS OF THE ATOMS. 



159 





The molecule H 2 S0 4 is inherent^ polarized and induces at once a 
similar condition in the normally neutral molecule Zn. At the poles of 
each of these molecules we have therefore free electricity. When now Zn 
replaces H 2 in H 2 S(> i it takes with it into its new combination only free 
positive electricity, leaving behind the comsponding negative electricity 
on the adja enr, molecule of zinc. Meanwhile the hydrogen atoms thus 
liberated bring with them to form the molecule H-1I only po»i ive elec- 
tric ity. We have thus set free on opposite molecules at the same time 
equivalent quantities of the two electricities, and the equilibrium being 
thus disturbed, an interchange at once takes place between them, by 
which the normal condition of their atmospheres is restored. In order 
to make this point clearer, we have endeavored to illustrate the reaction in 
the following diagram : — 

H 2 =S 4 Zn Zn 

Factors 



Products 



This diagram, however, indicates very imperfectly the conception we 
have formed of the process, and there are certain quantitative relations 
between the parts which must not be overlooked, although they can be 
as yet but very imperfectly understood. We should naturally infer that 
the quantity of ethereal atmosphere would be determined in every case by 
the mass of the molecule, but the quantities of free electricities separated 
irom this atmosphere under different conditions seem to depend on the 
atomicities of the radicals of which the molecule consists. At least, the 
facts indicate that the amount of free electricity which any group of 
atoms takes out of the molecule from which it is parted is exactly meas- 
ured by the number of atomic bonds thus broken. Hence in our diagram 
the amount of positive electricity which H % takes from H.,80^ is a defi- 
nite quantity and exactly equal to that which Zn carries in to take its 
place. Moreover, this last quantity came orirrinaHv, not from one, but 
from two zinc molecules, and the chemical metathesis between II 2 and 
Zn was accompanied by an interchange of electricities between the zinc 
molecules, by which all the free positive electricity passed to the one 
which entered into combination, and all the free negative ele-t'icity to 
the one left behind ; and further, as already stated, this free negative elec- 
tricity is equivalent to the free positive electricity on the hydrogen mole- 
cule formed at the same time. 

If, as in the usual form of the reaction we have been studying, the acid 
sufficiently diluted is poured upon clippings of sheet zinc, it is found that, 
although the mass of the metal is polarized throughout, the. polarity is 
very irregularly distributed. A multitude of negative polar points "are 
formed upon the surface, from which bubbles of hydrogen gas arc evolved, 
and around these are spaces positively polarized where the metal enters 
into solution. According to our theory, when the molecules of metal re- 
pla"e the atoms of hydrogen they take with them positive electrical 
charges, leaving behind equivalent negative charges, and these are trans- 
mitted from molecule to molecule of the metal, until they reach one of 
the negative polar points above mentioned. It is there that the inter- 
change takes place with the positive charges on the molecules of hydro- 
gen gas as rapiddy as these are formed. The polar points just referred 
to appear to be determined by variations of texture or bits of impurity 




1G0 ELECTRICAL RELATIONS OF THE ATOMS. 

in the metal, and this is the reason that the creneral polarity of the macs 
is so irregularly distributed. If the rmtal is absolutely pure and inn- 
form in texture, or if the surface of the common sheet zinc is previously 
amalgamated, there is no local action, and the zinc will not dissolve unless 
we fasten to the metal a piece of some material less readily acted on by 
the acid, which must be also a conductor of electricity. But when this is 
done, the whole mass becomes polarized uniformly throughout, after the 
pattern represented in Fi<r. 77 b. Of this system the surface of the zinc 
forms the positive pole, and the surface of the second material the nega- 
tive pole. Chemical action ensues as before, and while zinc dissolves at 
the positive pole, hydrogen gas is evolved from the negative pole. 

We are now prepared to understand the conditions in the Voltaic cell 
represented in Fig. 77. Here we have a plate of zinc and a plate of pla- 
tinum, united by a metallic wire and dipping together into the acid liquid, 
with their surfaces opposed to each other and not touching Here, also, 
the two plates with the conductor form one uniformly polarized system, 
of which the surface of the zinc is the positive and the surface of the pla- 
tinum the negative pole. The polarity of this arrangement is in need 
by the action of the acid, whose molecules are inherently polarized. 
Moreover, under these conditions the mass of acid be- 
J^ 8 ' tween the plates forms also a uniformly polarized 

system, the molecules arranging themselves in polar 
lines as represented in Fig 78. We may compare 
the combination thus formed to a magnetic circuit, 
consisting of a horseshoe magnet and its armature, 
or rather of a bar magnet wi h a horseshoe armature. 
The inherently polarized liquid corn sponds to the 
permanent magnet, the system of metallic plates to 
the armature with its induced polarity. Now just as in the magnetic cir- 
cuit we have a strong attractive force at the surfaces where the armature 
touches the magnet, so in the Voltaic circuit we have a powerful force 
exerted at each of the corresponding surfaces. A mutual attraction is 
exerted between the hydrogen end of the acid molecule and the platinum 
surface on one side, and the sulphion end 1 of the same molecules and 
the zinc surface on the other side. These forces are adequate to decom- 
pose the arid. The sulphion atoms enter into union with the zinc 
to form zincic sulphate, which dissolves in the acid liquid, while the hy- 
drogen atoms combine with each other to form molecules of hydrogen 
gas, which collects in bubbles that rise along the surface of the platinum 
plate. Meanwhile, every molecule of zinc which enters into solution 
leaves behind a charge of negative electricity, and every molecule of hy- 
drogen gas carries to the surface of the platinum plate a charge of posi- 
tive electricity, and these opposite charges flow together through the con- 
ductor, forming what we call an electrical current, which tends to restore 
the electrical equilibrium that the chemical action destroys. 

Electrical Current. According to our theory an electrical current con- 
sists in the- last analysis in the transfer of the ethereal medium between 
neighboring molecules, the one giving up a quantity of positive electricity 
and receiving an equivalent portion of negative electricity in its stead. This 
transfer is supposed to take place at the surface of contacr between the molec- 
ular atmospheres by a process similar to diffusion (58), and implies an 
oscillation of the molecules by which each is brought alternately in near 
proximity to its neighbors on either side. The oscillatory motion is 
maintained by the alternate attractions and repulsions, which the varying 
phases of the molecules necessarily determine, and is a most important 

1 For the sake of simplicity we have represented in the figures molecules 
of E- CI instead of H^S t , but the theory applies equally to both. 



ELECTRICAL RELATIONS OF THE ATOMS. 161 

clement of the electrical current. It can easily be inrtated by suspending 
with silk threads small metallic balls between two bras- knobs connected 
with the conductors of an electrical machine, so that they hang near but 
at equally small distances from each o heron the same line. The continu- 
ous oscillation of these balls, while the machine is in action, illustrates what 
we conceive to be ihe mode of motion in t ie molecules of a conductor. 

If the above explanation is correct, it is obvious th it an electrical cur- 
rent in a solid conductor has two distinct elements: first, an oscillatory 
motion ol the molecules; secondly, a mutual transfer of the two modifica- 
tions of theele trical ether from molecule to molecule, along the lines unit- 
ing the opposite poles of the polar system, which every current implies. 
But in the acid liquid, which not only originates the current but also 
forms a part of the circuit, the relations are somewhar different. There 
the transfer of the two electricities is attended with a decomposition of the 
acid molecules, and the opposed atoms, each bearing its charge of elec- 
tricity, actually travel from one plate to the other. Thus we have the 
singular phenomenon produced of two coexisting atomic currents through- 
out the mass of the liquid, a stream of sulphion atoms constantly setting 
towards the zinc plate, and a stream of hydrogen atoms flowing in the 
opposite direction in the same space towards the platinum plate. The 
result is producd by a constant metathesis along the who e line of mole- 
cules between the two plates, so that for every atom of sulph on which 
enters into union with the zinc a double atom- or mokcule of hydrogen 
is set free at the face of the platinum plate. 

As our theory shows, the opposite currents of atoms in the liquid and 
the opposite curr nts of electricity in the solid conductor are mutually 
dependent. Hence, if the connection is broken so that the mo ion can 
no longer be transmuted through the conductor, the motion in the liquid 
itself ceases; and if by any means the mo ion through the conductor is 
checked the morion of the atoms in the liquid is red iced to the same ex- 
tent. The two currents, which, as we have seen, are continuous through- 
out the whole circuit, take the names of the two kinds of electricity which 
they respectively carry ; that flowing into the conducting wire from the 
platinum, or inactive plate, being called the po itive current, and that 
from the zinc, or active plate, the negative current. Reasoning from cer- 
tain mechanical phenomena, the physicists originally conclud d that the 
electrical current flowed in but one dhvetion, that is, through the con- 
ducting wire from the platinum plate to the zinc, and from the zinc plate 
through the lipiid back again to the platinum; and now, when the direc- 
tion of t ie current is spoken of, it is this direction, that of the positive 
current, which is always meant. 

87. Electrical Conducting Power or Resistance. — Different 
materials transmit the electric current with very different de- 
grees of facility ; for while in some this peculiar form of molec- 
ular motion is easily maintained, in others the molecules yield 
to it only with difficulty, and many substances seem not to be 
susceptible of it. The conducting powers of different metallic 
wires have been very carefully studied, and some of the most 
trustworthy results are collected in the following table. Silver 
is the best conductor known, and, assuming that a silver wire of 
definite size and 100 centimetres long is taken as the standard, 
the number oppo.-ite the name of each metal is the length in 
centimetres of a wire made of this metal, and of the same size 
11 



162 



ELECTRICAL RELATIONS OF THE ATOMS. 



as the first, which will oppose the same resistance to the trans- 
mission of the current. The second column gives the relative 
resistances of wires of the same materials when of equal size 
and of equal lengths. The relative or specific resistances of two 
such wires must evidently be inversely proportional to their 
conducting powers, and thus the numbers of the second column 
are easily calculated from those of the first. For the results 
collated in this table we are indebted to the careful investiga- 
tions of Professor Matthiessen. 



Pure Metals. 


Conducting Power. 


Specific Resistance. 




At0°. At 100°. 


At 0°. At 100°. 


Silver (hard drawn) 


100.00 71.56 


1.000 1.397 


Copper (hard drawn) 


99.95 70.27 


1.0005 1.423 


Gold (hard drawn) 


77.96 5590 


1.233 1.788 


Zinc 


29.02 20.67 


3 445 4.838 


Cadmium 


23.72 16.77 


4.216 5.964 


Cobalt 


17.22 




5.808 


Iron (hard drawn) 


16.81 




5.948 


Nickel 


13.11 




7.628 


Tin 


12.36 


8.67 


8091 11.53 


Thallium 


9.16 




10.92 


Lead 


8.32 


5.86 


12.02 17.06 


Arsenic 


4.76 


3.33 


21.01 30 03 


Antimony 


• 4 62 


3.26 


21.65 30.68 


Bismuth 


1 .245 


0.878 


80.34 113.9 


Commercial 
Metals. 


C.P. 


Sp. R. 


(P. 


Commercial 
Metals. 


C.P. 


Sp. R. 


Co. 


Copper 


77.43 


1.291 18.8 


Iron 


14.44 




6.924 


20.4 


Sodium 


37.43 


2.672 21.7 


Palladium 


12.64 




7.911 


17.2 


Aluminum 


33.76 


2.962 19 5 


Platinum 


10.53 




9.497 


20.7 


Magnesium 


25.47 


3.926 17.0 


Strontium 


6.71 




14.90 


20.5 


Calcium 


22.14 


4.516 16> 


Mercury 


1.63 




61.35 


22.8 


Potassium 


20.85 


4.795 20.4 


Tellurium 


0.000 


"7 


129,800 


19.6 


Lithium 


19.00 


5.262 20.0 


Red Phosphorus 


0.00000123 81,300,000 24.0 



If, next, we compare wires of the same material, but of dif- 
ferent sizes, we find that the resistance increases as the length, 
and diminishes as the area, of the section. Moreover, if we 
adopt some absolute standard of resistance, like that selected by 
the English physicists, we can easily express the resistance of 
any given conductor in terms of this unit. It must be remem- 
bered, however, in making such comparisons, that the resist- 
ance varies with the temperature, and also that the conducting 
power of the same metal is materially influenced both by its 
physical condition and by the presence of impurities. 



ELECTRICAL RELATIONS OF THE ATOMS. 163 

88. Ohm's Law. — The first effect of the chemical forces in 
the cell of an electrical combination is to marshal the dis.-imilar 
atoms of the active liquid between the plates into lines, which 
at once begin to move in parallel columns, but in opposite di- 
rections (Fig. 78). Moreover, each one of these lines of moving 
atoms is continued by a corresponding line of oscillating atoms 
in the conducting wire, and thus is formed a continuous circuit 
returning upon itself. The union of all the lines of force in 
the two opposite coexisting streams constitutes in any case the 
electrical current, and the different parts of this continuous chain 
are so related that the total amount of motion is always the same 
at every point on the circuit, and no more lines of moving atoms 
form in the liquid between the platts than can be continued 
through the oscillating atoms of the solid conductors. 

If we adopt this theory, it is obvious that the strength of any 
electrical current must depend, — first, on the number of con- 
tinuous lines of force, and secondly, on the strength of the 
polarity transmitted through each of these channels. Of these 
two elements, the first is determined solely by the total resist- 
ance which the various parts of the circuit oppose to the elec- 
trical motion, and the greater this resistance the less will be 
the number of the lines of force. The second element is de- 
termined by the value of the resultants of all the polar forces 
acting in any combination, which draw the dissimilar atoms 
towards the opposite plates, — a value which depends solely on 
the chemical relations of the materials of the plates to that of the 
active liquid, and is what is called the electromotive force of the 
combination, a quantity we will represent by E. 

It appears, then, from the above analysis, that an electrical 
current is a continuous chain, which is sustained in a regulated 
and equable motion in all its parts by the chemical activity in 
the cell, and that the strength of this current at any point of the 
chain must be directly proportional to the electromotive force, 
and inversely proportional to the sum of the resistances through- 
out the circuit. If, then, we represent the resistance in the con- 
ducting wire by r, the resistance of the liquid between the plates 
of the cell by i?, 1 and also the strength of the current by G } we 
shall have, in every case, 

1 The resistance of any circuit may be conveniently divided into two parts, 



164 ELECTRICAL RELATIONS OF THE ATOMS. 

The quantities (7, R, r, and E may all be accurately measured, 
and stand in each case for a certain number of arbitrary units, 
whose relations will hereafter be stated. 

89. Electromotive Force and Strength of Current. — It would 
seem at first sight as if the strength of an electric current might 
be increased by simply enlarging the size of the plates in the 
combination employed, and obviously the number of possible 
lines of moving atoms which could be marshalled in the liquid 
between the plates would thus be increased; but, as has been 
stated, the parts of the circuit are so intimately connected that 
no greater number of lines of atoms can form between the plates 
than can be continued through the whole circuit, and practically 
there may be formed between the smallest plates a vastly greater 
number of atomic lines than can be continued through any con- 
ductor, however good its quality or however ample its size. 
Hence it is, that by increasing the size of the plates we mul- 
tiply the lines of force only in so far as we thereby lessen the 
resistance in the liquid part of the circuit. "We thus simply 
lessen the value of E in Ohm's formula [02] ; but if ihis value 
is already small as compared with r, that is, if the resistance in 
the cell is small compared with that in the conductor, no mate-- 
rial gain in the power of the current, or in the value of C, will 
result. On the other hand, if the exterior resistance, r, is small, 
or nearly nothing, as when the plates are connected by a thick 
metallic conductor, then the value of C will increase in very 
nearly the same proportion as the size of the plates is enlarged, 
and the value of i?, in consequence, diminished. Under these 
conditions, the number of lines of moving atoms is greatly mul- 
tiplied, and we obtain a current of very great volume, but only 
flowing with the limited force which the single cell is capable 
of maintaining. Such a current has but little power of over- 
coming obstacles ; and if w<e attempt to condense it by using a 
smaller conductor, we reduce, as has been said, the chemical 
action which keeps the whole in motion, and thus lessen the 
volume of the flow. This is generally expressed by saying 

first, the resistance of the conducting wire, and secondly, the resistance of the 
liquid portion of the circuit between the two plates of the cell. The resistance 
of the solid conductor may be readily estimated on the principles stated in the 
last section, and the resistance of liquid may be measured in a similar way. 
The last depends, — 1. On the conducting power of the liquid; 2. On the length 
of the liquid circuit, which is determined by the distance apart of the plates; 
3. On the area of the section of the liquid conductor, which is determined by 
the size of the plates ; and, 4. On the temperature. 



ELECTRICAL RELATIONS OF THE ATOMS. 165 

that the current has large quantity, but small intensity, or more 
properly, electromotive power. 

It must now be obvious from the theory, that we cannot in- 
crease effectively the intensity of a current (its power of over- 
coming obstacles) without in some way increasing the chemical 
activity, or, in other words, the electro-motive force of the com- 
bination employed, and Ohm's formula leads to the same result. 
If the value of r in our formula is very large as compared 
with R, we cannot increase it still farther without lessening the 
total value, C, unless at the same time we increase the value 
of E. Now, this electro-motive force may be, to a certain ex- 
tent, increased by using a more active combination ; but the 
limit in this direction is soon reached, and the construction of 
the cell which has been found practically to be the most effi- 
cient will be described below. 

We can, however, increase the effective electro-motive force 
to almost any extent by using a number of cells, and coupling 
them together in the manner represented by Fig. 79, the plati- 
num plate of the first cell being united by a large metallic con- 
nector to the zinc plate of the second, and so on through the 
line, until finally the external conductor establishes a connec- 
tion between the platinum plate of the last cell and the zinc 
plate of the first. Such a combination as this is called a Gal- 
vanic or Voltaic * battery, and the current which flows through 
such a combination has a vastly greater power of overcoming 
resistance than that of any single cell, however large. 

The increased effect obtained with such a combination will 
be easily understood, when it is remembered that each of the 
innumerable closed chains of 

J-jrr. 79. 

moving molecules now ex- 

tends through the whole /^---\ /—\ /— n /^~n\ 
combination, and that all its rfj} jW| rig FT{\ fcj] 
parts move in the same close H [R ^ Pj [FjJ 
mutual dependence as be- 
fore. But whereas with a single cell the motion throughout 
any single chain of molecules is sustained by the chemical 
energy at only one point, it is here reinforced at several points; 



* From the names cf Galvani and Volta, two Italian physicists, who first 
investigated this class of phenomena. 



166 ELECTRICAL RELATIONS OF THE ATOMS. 

and the polar energy at any point of the circuit is the effect of 
the induction of the acid molecules between each pair of plates 
concurring with that produced by the similar molecules between 
every other pair. The electro-motive power is then increased 
in proportion to the number of cells; and the effect on the cur- 
rent would be increased in the same proportion, were it not for 
the fact that the current must keep in motion a greater mass of 
liquid, and hence the resistance is increased at the same time. 
The value of this resistance, however, is easily estimated, since 
it is directly proportional to the distance through which the cur- 
rent has to flow in the liquid ; and hence, if the liquid is the 
same in all the cells, and the plates are at the same distance 
apart in each, the liquid resistance will be n times as great in a 
combination of n cells as it is in one. Moreover, since the effec- 
tive electro-motive force is n times as great also, while the ex- 
ternal resistance remains unchanged, the strength of the current 
from such a combination will still be expressed by formula [62] 
slightly modified. 

C=-p*4- [68] 

nR -f- r L J 

This formula shows at once, that, when the exterior resist- 
ance is very small, or nothing, very little or no gain will result 
from increasing the number of cells, for the ratio of nE to nR 
is the fame as that of E to R ; and, under such conditions, in 
order to increase the strength of the current, we must increase 
the surface of the plates. If, on the contrary, the exterior re- 
sistance is very large, the formula shows that great gain will 
- result from increasing the number of the cells, and that little 
or no advantage will accrue from enlarging the surface of the 
plates. Moreover, the formula enables us in any case to de- 
termine what proportion the number of cells should bear to the 
size of the plates in order to obtain the full effect of any battery 
in doing a given work; and in the numerous applications of 
electricity in the arts we find abundant illustrations of the 
principles it involves. The methods used in finding the values 
of the quantities represented in the formula lie beyond the 
scope of this work, and for such information the student is re- 
ferred to works on Physics. 

90. Constructions of Cells. — It is found practically that the 



ELECTRICAL RELATIONS OF THE ATOMS. 167 

simple combination of plates and acid first described must be 
slightly modified in order to obtain the best results. 

In the first place, both the zinc and sulphuric acid of com- 
merce contain impurities, which give rise to what is called 
local action, and cause the zinc to dissolve in the acid when 
the battery is not in action. Fortunately, however, it has been 
found that such local action can be wholly prevented by care- 
fully amalgamating the surface of the zinc and filtering the 
acidulated water. 

The mercury on the surface of the zinc plates acts as a sol- 
vent, and gives a certain freedom of motion to the particles 
of the metal. These, by the action of the polar forces, are 
brought to the surface of the plate, while the impurities are 
forced back towards the interior, so that the plate constantly 
exposes a surface of pure zinc to the action of the acid. 

By filtering we remove the particles of plumbic sulphate 
which remain floating in the sulphuric acid for a long time 
after it has been diluted with water, and which, when deposited 
on the surface of the zinc, become points of local action, even 
when the plates have been carefully amalgamated. 

In the second place, the continued action of the simple com- 
bination first described develops conditions which soon greatly 
impair, and at last wholly destroy, its efficiency. 

The hydrogen gas, which by the action of the current is 
evolved at the platinum plate, adheres strongly to its surface, 
and with its powerful affinities draws back the lines of atoms 
moving towards the zinc plate, and thus diminishes the effec- 
tive electro-motive force. Moreover, after the battery has been 
working for some time, the water becomes charged with zincic 
sulphate ; and then the zinc, following the course of the hydro- 
gen, is also deposited on the surface of the platinum, which 
after a while becomes, to all intents and purposes, a second 
zinc plate, and then, of course, the electric current ceases. 

Both of these difficulties, however, have also been sur- 
mounted by a very simple means discovered by Mr. Grove, of 
London. The Grove cell, Fig. 80, consists of a circular plate of 
zinc well amalgamated on its surface, and immersed in a glass 
jar containing dilute sulphuric acid. Within the zinc cylinder is 
placed a cylindrical vessel of much smaller diameter, made of 
porous earthenware, and filled with the strongest nitric acid, 



168 



ELECTRICAL RELATIONS OF THE ATOMS. 



and in this hangs the plate of platinum, Fig. 81. The. walls of 

Fig. 81. 





the porous cell allow both the hydrogen and the zinc atoms to 
pass freely on their way to the platinum plate ; but the moment 
they reach the nitric acid they are at once oxidized, and thus 
the surface of the platinum is kept clean, and the cell in condi- 
tion to exert its maximum electro-motive power. In this com- 
bination we may substitute for the plate of platinum a plate 
of dense coke, such as forms in the interior of the gas retorts, 
which is very much cheaper, and enables us to construct large 
cells at a moderate cost. The use of gas coke was first sug- 
gested by Professor Bunsen of Heidelberg, and the cell so 
constructed generally bears his name. The Bunsen cell, such 
as is represented in Fig. 82, is exceedingly well adapted for use 

Fig. 82. 




in the laboratory. These cells are usually made of nearly a 



ELECTRICAL RELATIONS OF THE ATOMS. 169 

uniform size, the zinc cylinders being about 8 c. m. in diameter 
by 22 c. m. high, and they are frequently referred to as a rough 
standard of electrical power. They may be united so as to 
produce effects either of intensity or of quantity. The inten- 
sity effects are obtained in the manner already described (see 
Fig. 79), and the quantity effects are obtained with equal readi- 
ness ; since by attaching the zinc of several cells to the same 
metallic conductor, and the corresponding coke plates to a 
similar conductor, we have the equivalent of one cell with large 
plates. Many other forms of battery, differing in more or less 
important details from those here described, and adapted to 
special applications of electricity, are used in the arts, and are 
fully de.-cribed in the larger works on physics. 

91. Electrolysis. — As our theory indicates, the electrical 
current has the remarkable power of imparting to the unlike 
atoms of almost all compound bodies motion in opposite direc- 
tions, like that in the battery cell itself, and this, too, at what- 
ever point in the circuit they may be introduced. The galvanic 
battery thus becomes a most potent agent in producing chemi- 
cal decompositions, and it is in consequence of this fact that the 
theory of the instrument fills such an important place in the phi- 
losophy of chemistry. 

If we break the metallic conductor at any point of a closed 
circuit, the two ends, which in chemical experiments we usually 
arm with platinum plates, 1 are called poles. The end con- 
nected with the platinum or coke plate, from which the positive 
current is assumed to flow, is called the positive pole, and the 
end connected with the zinc plate, from which the negative 
current flows, is called the negative pole. Let us assume 
that Fig. 83 represents the two platinum poles dipping in a 
solution of hydrochloric acid in water, which 
thus becomes a part of the circuit. The Fi s- 83 - 

moment the circuit is thus closed, the if and 
CI atoms begin to travel in opposite direc- 
tions, just as in the battery cell below. The 
hydrogen atoms move with the positive cur- 
rent towards the negative pole, and hydro- Ihhhhhhh 
gen gas is disengaged from the surface of 

1 We u«e platinum plates because this metal does not readily enter into 
combination with the ordinary chemical agents. 



ci a ci ci ci cial 



170 ELECTRICAL RELATIONS OF THE ATOMS. 

the negative plate, while the chlorine atoms move with the 
negative current towards the positive pole, and chlorine gas 
is evolved from the surface of the positive plate. More- 
over, it will be noticed that each kind of atoms moves in the 
same direction on the closed circuit, that is, follows the course 
of the same current, both in the battery cell below and in the 
decomposing cell above ; and wherever we break the circuit, 
and at as many places as we may break it, the same phenomena 
may be produced, provided only that our battery has sufficient 
power to overcome the resistance thus introduced. 

If next we dip the poles in water, the atoms of the water 
will be set moving, as shown in Fi<r. 84; hy- 

Fi<*. 84. . 

a c drogen gas escaping as before from the neg- 

IL ative pole, and oxygen gas from the positive. 
oooooo i W e nnc '' however, that pure water opposes 
H2H2H2H2H2H2J a very great resistance to the motion of the 
i current; and, unless the current has great 
intensity, the effects obtained are inconsider- 
able. But if we mix with the water a little sulphuric acid, the 
decomposition at once becomes very rapid ; but then it is the 
atoms of the sulphuric acid, and not those of the water, which 
are set in motion. The molecule ff 2 S0 4 divides into H 2 and 
SO±; the hydrogen atoms moving in the usual direction, and 
the atoms of SO^ in the opposite direction. As soon, however, 
as the last are set free at the positive pole, they come in 
contact with water, which they immediately decompose, 
2B 2 0+2SO i =2H 2 S0 4 + O--O, and the oxygen gas thus 
generated escapes from the face of the platinum plate. Thus 
the result is the same as if water were directly decomposed, 
but the actual process is quite different. 

So also in many other cases of electrolysis, — as these decom- 
positions by the electrical current are called, — the process is 
complicated by the reaction of the water, which is the usual 
medium employed in the experiments. Thus, if we interpose 
between the poles a solution of common salt,iV«C/, the chlorine 
atoms move towards the positive pole, and chlorine gas is there 
evolved as in the first example. The sodium atoms move also, 
but in the opposite direction. As soon, however, as they are 
set free at the negative pole, they decompose the water present; 
hydrogen gas is formed, which escapes in bubbles from the 






ELECTRICAL RELATIONS OF THE ATOMS. * 171 

platinum plate, while sodic hydrate (caustic soda) remains in 
solution, 

2H 2 + 2Na = 2H, Na-0-\~ R-H. 

"We add but one other example, which illustrates a very 
important application of these principles in the arts. We as- 
sume, in Fig. 85, that the positive 
pole is armed with a plate oF copper, ^ Flg- 8a ' 

and that to the negative pole has been I 

fastened a mould of some medallion c \ SOiS c ° i ^ 4 S0 J || 
we wish to copy, the surface of which, 1 * 

at least, is a good conductor. We 

assume further that both copper plate and mould are sus- 
pended in a solution of sulphate of copper, Cu=SO v In this 
case the atoms of the compound are set in motion as before. 
Those of ccpper accumulate on the surface of the mould ; and 
at last the coating will attain such thickness that it can be re- 
moved, furnishing an exact copy of the original medallion. 
Meanwhile the atoms of SO± have found at the positive 
pole a mass of copper, with whose atoms they have combined; 
and thus fresh sulphate of copper has been formed, and the 
solution replenished. The process has in effect consisted in 
a transfer of metal from the copper plate to the medallion ; 
and, by using appropriate solvents, silver and gold can be 
transferred and deposited in the same way. 

In all these processes of electrolysis, one remarkable fact has 
been observed, which has a very important bearing on the 
theory of the battery. If in any given circuit we introduce a 
number of decomposing cells, containing acidulated water, we 
find that in a given time exactly the same amount of gas is 
evolved in each ; thus proving, what we have thus far assumed, 
that the moving power is absolutely the same at all points on 
the circuit. Moreover, the amount of gas which is evolved 
from such a decomposing cell in the unit of time is an ac- 
curate measure of the strength of the current actually flowing 
in any circuit, and this mode of measuring the quantity of an 
electrical current is constantly used. 

We should infer from the facts already stated, and the prin- 
ciple has been confirmed by the most careful experiments, that 
the chemical changes which may take place at different points 



172 ' ELECTEICAL RELATIONS OF THE ATOMS. 

of the same closed circuit are always the exact equivalents of 
each other. If, for example, we have a series of Grove's cells, 
arranged as in Fig. 79, and interpose in the external circuit 
two decomposing cells, as in Figs. 84 and 85, we shall lind 
(provided there is no local action) that the weight of zinc dis- 
solved in each of the five Grove's cells is the exact chemical 
equivalent, (2G) not only of the weight of hydrogen gas evolved 
from the first decomposing cell, but al.-o of the weight of me- 
tallic copper deposited on the mould in the second. For every 
63.4 grammes of copper deposited, 2 grammes of hydrogen are 
evolved, and 65.2 grammes of zinc are dissolved in each cell 
of the battery. If there is also local action in the cells, the 
chemical change thus induced is added to the normal effect of 
the battery-current. 

This important principle (discovered by Faraday) is in entire 
harmony with the theory of electricity developed in this chap- 
ter. In the single Voltaic cell, Fig. 77, there is but one source 
of free electricity, which all flows through the same conductor, 
In a Voltaic battery, Fig. 79, there are as many sources of free 
electricity as there are separate cells ; but only the free elec- 
tricity received on the end plates flows through the longer con- 
ductor, 1 for that received on the intermediate plates becomes 
neutralized in the shorter conductors 1 uniting the cells. In 
either case, if a liquid forms a part of the principal conductor, 
as in Fig. 83, then the molecules of the liquid decomposed by 
the current become an additional source of electricity, and the 
currents flowing from the two ends of the battery are neutral- 
ized by the charges of electricity, which the atoms liberated from 
the electrolyte 2 bring with them to either electrode. 2 Thus, in 
Fig. 83, the positive electricity flowing from the inactive plate 
of the battery is neutralized by the negative electricity, which 
the chlorine atoms yield, and the negative electricity from the 
active plate of the battery by the positive electricity, which the 
hydrogen atoms yield. Now, since, according to our theory, the 
strength of a current is necessarily the same at all points of a 

1 It will be noticed that each of the five conductors in Fig. 79 sustains the 
same relation .? to the battery as a whole. 

2 Th° liquid submitted to electrolysis is frequently called an electrolyte, and 
the inactive po.es dipping into the liquid are also called tlectroaes. 



ELECTRICAL RELATIONS OF THE ATOMS. 173 

continuous circuit, however extended, and since the amount of 
electricity set free in the decomposing cell, as in the buttery 
cells, must be proportional to the number of atomic bonds 
broken (86), it is evident that it would require, for example, 
twice as many hydrogen as copper atoms, liberated on the face 
of an electrode in a, given time, to supply the same current, and 
this is equivalent to the principle stated above. 

The examples which have been given are sufficient to illus- 
trate the remarkable power which the electric current possesses 
of netting in motion the atoms of compound bodies. Innumer- 
able experiments have shown that, in reference to their rela- 
tions to the current, the atoms, both simple and compound, may 
be divided into two great classes : first, those which travel on 
the line of the circuit in the direction of the positive current 
and follow in the lead of the hydrogen atoms ; and, secondly, 
those which follow the lead of the chlorine atoms, and move in 
the opposite direction with the negative current. The first 
class of atoms, or radicals, we call positive ; and the second class, 
negative. 

The opposition in qualities of the chemical atoms, which the 
study of these electrical phenomena has revealed, is, in many 
cases at least, relative, and not absolute. For, while there are 
some atoms which always manifest the same character, there 
are others which appear in some associations positive, and in 
other associations negative. To such an extent is this true, 
that the electrical relations of the atoms are best shown by 
grouping the elements in series, which may be so arranged that 
each member of the series shall be electro-positive when in 
combination with those elements which follow it, and electro- 
negative when combined with those which precede it. 

Note. — Questions and problems bearing on this chapter will 
be found in the Appendix, page 567. 



CHAPTER XVI. 

RELATIONS OF THE ATOMS TO LIGHT. 

92. Light a Mode of Atomic Motion. — It has already been 
intimated (§ 61, note), that the phenomena of vision are the 
effects of an atomic motion transmitted from some luminous 
body to the eye through continuous lines of material particles, 
and such lines we call rays of light. This motion may origi- 
nate with the atoms of various substances ; but in order to 
explain its transmission, we are obliged to assume the existence 
of a medium filling all space, of extreme tenuity, and yet 
having an elasticity sufficiently great to transmit the luminous 
pulsations with the incredible velocity of 180.000 miles in a 
second of time. This medium we call the ether, but of its 
existence we have no definite knowledge except that obtained 
through the phenomena of light themselves, and these require 
assumptions in regard to the constitution of the ethereal medium 
which are not realized even approximately in the ordinary 
forms of matter ; for while the assumed medium must be 
vastly less dense than hydrogen, its elasticity must surpass that 
of steel. 

According to the undulatory theory, motion is transmitted 
from particle to particle along the line of each luminous wave 
very much in the same way that it passes along the line of 
ivory balls in the well-known experiment of mechanics. The 
ethereal atoms are thus thrown into waves, and the order of 
the phenomena is similar to that with which all are familiar 
in the grosser forms of wave motion. But in this connection 
we have no occasion to dwell on the mechanical conditions 
attending the transmission of the motion. The motion itself 
may be best conceived as an oscillation of each ether particle 
in a plane perpendicular to the direction of the ray, not 



RELATIONS OF THE ATOMS TO LIGHT. 175 

necessarily, however, in a straight line ; for the orbit of the 
oscillating molecule may be either a straight line, an ellipse, or a 
circle, as the case may be. Such oscillations may evidently 
differ both as regards their amplitude and their duration, and 
on these fundamental elements depend two important differences 
in the effect of the motion on the organs of vision, viz. intensity 
and quality, or brilliancy and color. 

If our theory is correct, it is obvious that the intensity of 
the luminous impression must depend upon the force of the 
atomic blows which are transmitted to the optic nerves, and it 
is also evident that this force must be proportional to the 
square of the velocity of the oscillating atoms, or what amounts 
to the same thing, to the square of the amplitude of the 
oscillation ; assuming, of course, that the oscillations are 
isochronous. 

The connection of color with the time of oscillation is not so 
obvious, and why it is that the waves of ether beating with 
greater or less rapidity on the retina should produce such 
sensations as those of violet, blue, yellow, or red, the physiologist 
is wholly unable to explain. We have, however, an analogous 
phenomenon in sound, for musical notes are simply the effects of 
waves of air beating in a similar way on the auditory nerves; 
and, as is well known, the greater the frequency of the beats, 
or, in other words, the more rapid the oscillations of the 
aerial molecules, the higher is the pitch of the note. Red 
color corresponds to low, and violet to high noes of music, 
and, the gradations of color between these extremes, passing 
through various shades of orange, yellow, green, blue, and 
indigo, correspond to the well-known gradations of musical 
pitch. 

From well-established data we are able to calculate the 
rapidity of the oscillations which produce the different sensa- 
tions of color, and also to estimate the corresponding lengths 
of the ether waves, and the following table contains the 
results. It must be understood, however, that these numbers 
merely correspond to a few shades of color definitely marked 
on the solar spectrum by certain dark lines hereafter to be men- 
tioned ; and that equally definite values may be assigned to 
the infinite number of intermediate shades which intervene 
between these arbitrary subdivisions of the chromatic scale. 



176 



KELATIONS OF THE ATOMS TO LIGHT. 



Number of waves or oscilla- 
tions in one second. 



Length of waves in frac- 
tions of a millimetre. 



477 


million 


million. 


650 millionths. 


506 


k 


K 


609 


u 


535 


a 


« 


576 


u 


577 


it 


u 


536 


a 


622 


a 


a 


498 


u 


658 


a 


a 


470 


a 


699 


a 


u 


442 


(i 



Color. 

Red 

Orange 

Yellow 

Green 

Blue 

Indigo 

Violet 

93. Natural Colors. — It follows, as a necessary consequence 
of the fundamental laws of mechanics, that an oscillating mole- 
cule can only transmit to its neighbor motion which is isochronous 
with its own. Hence a single ray of light can only produce a def- 
inite effect of color, and this quality of the ray will be preserved 
however far the motion may travel. A beam of light is simply 
a bundle of rays, and if the motion is isochronous in all its 
parts, that is, if the beam consists only of rays of one shade of 
color, such a beam will produce the simplest chromatic sensa- 
tion possible, — that of a pure color. If, however, the beam 
contains rays of different colors, we shall have a more complex 
effect, and the infinite variety of natural tints are thus produced. 
When, lastly, the beam contains rays of all the colors mingled 
in due proportion, we receive an impression in which no single 
color predominates, and this we call white light. 

The colors of natural objects, whether inherent or imparted 
by various dyes, are simply effects upon the retina produced by 
the beam after it has been reflected from the surface or trans- 
mitted through the mass of the body, and the peculiar chromatic 
effects are due to the unequal proportions in which the dif- 
ferent colored rays are thus absorbed. The color reflected, and 
that absorbed or transmitted, are always complementary to 
each other, and if mingled they would reproduce white. It is 
obvious, moreover, that no beam of light, however modified by 
reflection or transmission, could produce the sensation of a 
given color, if it did not contain from the first the correspond- 
ing colored rays. Hence it is that the colors of objects only 
appear naturally by daylight, and when illuminated by a 
monochromatic light, all colors blend in that of this one pure 
tint. 

94. Chromatic Spectra and Spectroscopes. — When a beam 
of light is passed through a glass prism placed as shown in Fig. 



i 



RELATIONS OF THE ATOMS TO LIGHT. 



177 



Fig. 86. 




86, it is not only refracted, that is, bent from its original rectilinear 
course, but the colored rays of which the beam consists, being 
bent unequally, are separated to a greater or less extent, and fall- 
ing on a screen produce an elongated image colored with a suc- 
cession of blending tints, which we call the spectrum. The red 
rays, which are bent the least, are said to be the least refran- 
gible, while the violet rays are the most refrangiblr, and inter- 
mediate between these we have, in the order of refrangibility, 
the various tints of orange, yellow, green, blue, and indigo. 
Thus a prism gives an easy means of analyzing a beam of 
light, and of discovering the character of the rays by which a 
given chromatic effect is produced. Such observations are 
very greatly facilitated by a class of instruments called spectro- 
scopes, and Figs. 87 and 90 will illustrate the principles of 
their construction. 

In the very powerful instrument first represented, the beam 
of light is passed in succession through nine prisms (each 
having an angle of 45°), and the extreme rays are thus widely 
separated, while the beam itself is bent around nearly a whole 
circumference. The only other essential parts of the instru- 
ment are the collimator A and the telescope B. The light first 
enters the collimator through a narrow slit, and having passed 
through the prisms is received by the telescope. The tele- 
scope is adjusted as it would be for viewing distant objects, 






178 



RELATIONS OF THE ATOMS TO LIGHT. 



and a lens at the end of the collimator serves to render the 
rajs diverging from the slit parallel, so that when the two 

Fig. 87. 




tubes are in line, one sees through the telescope a mag- 
nified image of the slit, just as if the slit were at a great 



Fig. 88. 




distance. In like manner when the telescopes are placed as 
in Fig. 88, and when the light before reaching the telescope 



RELATIONS OF THE ATOMS TO LIGHT. 179 




111 



■HHIl 




Inge. I low. | 

passes through the whole series of prisms, we still see a single 
definite image whenever the slit is illuminated by a pure 
monochromatic light. Moreover, this image has a definite 
position in the field of view, which, when the instrument is 
similarly adjusted, depends solely on the refrangibility of the 
light. 

Thus, if we place in front of the slit a sodium flame, which 
emits a pure yellow light, Ave see a single yellow image of this 
longitudinal opening, as in Fig. 89, Na. If we use a lithium 
flame, we see a similar image, 1 but colored red, and at some 
distance from the first, to the left, if the parts of our in- 
strument are disposed as in Fig. 88. If we use a thalium 
flame, we in like manner see a single image, but colored 
green, and falling considerably to the right of botli of the 
other two. If now we illuminate the slit by the three 
flames simultaneously, we see all three images at once in the 
same relative position as before. So also if we examine the 
i The second image shown in Fig. 89, Li is not ordinarily seen. 



180 RELATIONS OF THE ATOMS TO LIGHT. 

flame of a metal, which emits rays of several definite degrees 
of refrangibility, we see an equal number of definite images 
of the slit. If, next, we illuminate the slit with sunlight, 
which contains rays of all degrees of refrangibility, we see an 
infinite number of images of the slit spread out along the field 
of view, and these, overlapping each other, form that continuous 
band of blending colors which we call the solar spectrum. If, 
lastly, we examine with our instrument the light reflected from 
a colored surface, or transmitted through a colored medium, 
we aho see a band of blending colors, but at the same time we 
observe that, certain portions of the normal solar spectrum are 
either wholly wanting or greatly obscured. 

With a spectroscope of many prisms like the one represented 
by Fig. 87, we can only see a small portion of the spectrum at 
once. By moving the telescope, which, fastened to a metallic 
arm, revolves around the axis of the instrument, different 
portions of the spectrum may be brought into the field of view ; 
while a vernier, attached to the same arm and moving over a 
graduated arc, enables us to fix the position of the spectrum 
lines, as the images of the slit are usually called. The other 
mechanical details shown in the figure are required in order 
to adjust the various parts of the instrument, and especially in 
order to bring the prisms to what is termed the angle of 
minimum deviation. But an instrument of this magnitude and 
power is not required for the ordinary applications of the 
spectroscope in chemistry. For this purpose a small instru- 
ment consisting of a collimator, a single prism, and a telescope, 
all in a fixed position, are amply sufficient. In the field of such 
a spectroscope the whole spectrum may be seen at once ; and 
the position of the spectrum lines is very easily determined by 
means of a photographic scale placed at one side, and seen by 
light reflected into the telescope from the face of the prism. 

The various parts of the instrument, as arranged for ob- 
servation, are shown in Fig. 90. A is the collimator, P the 
pri^m, and B the telescope. The tube C carries the photo- 
graphic scale, and has at the end nearest to the prism a 
lens of such focal length that the image both of the slit and 
the scale may be seen through the telescope at the same time, 
the one appearing projected upon the other. The screw e 
serves to adjust the width of the slit. Moreover, one half of the 



RELATIONS OF THE ATOMS TO LIGHT. 181 

Fig. 90. 




length of the slit is covered by a small gla<=s prism so arranged 
that it reflects into the collimator tube the rays from a lamp 
placed on one side. Thus the two halves of the slit may be 
illuminated independently by light from different sources, and 
the two spectra, which are then seen superimposed upon each 
other (see Fig. 01), exactly compared. The various screws, 
which appear in Fig. 90, are u ? ed for adjusting the different 
parts of the instrument. 

95. Spectrum Analysis. — The atoms of the different chem- 
ical elements, when rendered luminous under certain definite 
conditions, always emit light whose color is more or less 
characteristic, and which, when analyzed with the spectroscope, 
exhibit spectra similar to those which are represented in Fig. 
89, so far as is possible without the aid of color. Sometimes 
we see only a single line in a definite position, as in the case 
of Na, Li, and Th, already referred to. At other times 
there are several such lines ; and, still more frequently, to 
these lines (or definite images of the slit) there are super- 
added more or less extended portions of a continuous spectrum. 
Moreover, not only is the general aspect of each spectrum 
exceedingly characteristic, but also the occurrence of its 
peculiar lines is, so far as we know, an absolute proof of the 



182 RELATIONS OF THE ATOMS TO LIGHT. 

presence of a given element, and these lines may be readily 
recognized by their position, even when the character of the 
spectrum is otherwise obscure. It is evident then that we 
have here a principle which admits of most important ap- 
plications in chemical analysis, and it only remains to con- 
sider under what conditions the elementary atoms emit their 
characteristic light. 

First. All bodies when intensely heated are rendered lumi- 
nous, and, other things being equal, the higher the temperature 
the more intense is the light. The brilliancy of the light 
emitted at the same temperature by different bodies varies 
very greatly, the densest bodies being, as a general rule, the 
mo-t intensely luminous. 

Secondly. — Solid and liquid bodies, if opaque, emit when 
ignited white light, or at least light which shows with the spec- 
troscope a continuous spectrum more or less extended. At a 
red heat the light from such bodies consists chiefly of red rays, 
but as the temperature rises first to a white and then to a blue 
heat, the more refrangible rays become more abundant and 
finally predominate. 

Thirdly. — The elementary substances give out their pecu- 
liar and characteristic light only in the state of gas or vapor. 
Hence, when we examine with a spectroscope a source of light, 
we may infer that a continuous spectrum indicates the presence 
of solid or liquid bodies, while a discontinuous spectrum, with 
definite lines or images of the slit, indicates the presence of 
gases and vapors ; and in the last case we can, as has been seen, 
infer from the position of the lines the nature of the luminous 
atoms. It would seem, however, from recent investigations, 
that under certain conditions even a gas may show a continu- 
ous spectrum, and there are other seeming exceptions which 
admonish us that the general principles just stated should be 
applied with caution. 

FourtJtly. — At the very high temperatures at which alone 
gases or vapors become luminous, compound bodies, as a rule, 
appear to be decomposed, and the elementary atoms disasso- 
ciated. Hence the observations with the spectroscope have 
been almost entirely confined to the spectra of the elementary 
substances, and our knowledge of the spectra of compound sub- 
stances is exceedingly limited. In some few cases where the 



RELATIONS OF THE ATOMS TO LIGHT. 183 

spectrum of a compound has been obtained, it has been noticed 
that, as the temperature ri-es, this spectrum is suddenly re- 
solved into the separate spectra of the elements of which the 
compound consists. 

Fifthly. — At a high temperature the metallic atoms of a 
compound body are far more luminous than tho-e of the other 
elementary atoms with which they are associated. Hence, 
when the vapor of a metallic compound is rendered luminous, 
the light emitted is so exclusively that of the metallic atoms, 
disassociated by the heat, that when examined with the spec- 
troscope the spectrum of the metal is alone seen ; and this is 
the probable explanation of the fact that the salts of the same 
metal, when treated as will be described in the next para- 
graph, all show, as a general rule, the same spectrum as the 
metal itself. 

Lastly. — The substance, on which we wish to experiment, 
may be rendered luminous in several ways. If the substance 
is a volatile metallic salt, the simplest method is to expose a 
bead of the substance (supported on a loop of platinum wire) 
to the flame of a Bu^en's burner (Fig. 90), which by itself 
burns with a nearly non-luminous flame. The flame soon be- 
comes filled with the disassociated atoms of the metal and 
shines with their peculiar light. 

In order to study the spectra of the less volatile metals like 
aluminum, iron, or nickel, we u>e two needles of the metal, and 
pass between the points, when about one fourth of an inch 
apart, the electric discharges of a powerful RuhmkorfF coil, 
condensed by a large Leyden jar. The metal is volatilized 
by the heat of the electric current, and the space between the 
points becomes filled with the intensely ignited vapor, which 
then shines with its characteristic light." 1 

In a similar way we can experiment on the permanent gases 
and lighter vapors, enclosing them in a glass tube with plati- 
num electrodes, and before sealing the tube reducing the ten- 
sion with an air pump, when the discharge will pass through 
a length of several inches of the attenuated gas. The light 
then emitted comes from the atoms or molecules of the ga-, and 
where the electric current is condensed as in the capillary por- 

1 An electric spark is in every case merely a line of material particles ren- 
dered luminous by the current. 



184 RELATIONS OF THE ATOMS TO LIGHT. 

tion of the tubes constructed for this purpose, the light is suf- 
ficiently intense to be analyzed with the spectroscope. 

The three different modes of experimenting just described do 
not by any means always give the same spectrum when ap- 
plied to the same chemical element. It constantly happens 
that as the temperature rises new lines appear, which are usu- 
ally those corresponding to the more refrangible rays, and at 
the very high temperatures generated by the electric discharge 
many of the spectra change their whole aspect. The ill-defined 
broad bands or luminous spaces which are so conspicuous at a 
low temperature (see Fig. 89), disappear, and are replaced by 
a greater or less number of definite spectrum lines. Gen- 
erally, however, the characteristic lines which mark the ele- 
ment at the lower temperature are seen also at the higher; but 
sometimes there is a sudden and complete change of the whole 
spectrum. The cause of these differences is not understood, 
but it has been thought by some investigators that the normal 
spectra of the elementary atoms consist of bright bands alone, 
and that the more or less continuous spectra, which are also 
seen at the lower temperatures, are to be referred to the im- 
perfect disassociation of the atoms, whose mutual attractions 
or partial combinations produce a state of aggregation ap- 
proaching the condition which determines the continuous spec- 
tra of liquid or solid bodies. 

96. Delicacy of the Method. - — Having now stated the 
general principles of spectrum analysis, and the conditions 
under which these principles may be applied, it need only be 
added that the method is one of extreme delicacy. It enables 
us to detect wonderfully minute quantities of many of the 
metallic elements, and has already led to the discovery of four 
elements of this class which had eluded all methods of investi- 
gation previously employed. The names of these elements, 
Rubidium, Caelum, Thallium and Indium, all refer to the 
color of their most characteristic spectrum bands. 1 

97. Solar and Stellar Chemistry. — ^ When a beam of sun- 
light is examined with a powerful spectroscope, the solar 
spectrum is seen to be crossed by- an almost countless number 
of dark lines distributed with no apparent regularity, and dif- 

1 The different bands of the same element are usually distinguished by 
Greek letters, 'following the order of relative brilliancy. 



RELATIONS OF THE ATOMS TO LIGHT. 



185 



fering very greatly in relative strength or intensity. These 
lines were first accurately described by the German optician 
Fraunhofer, and have since been known as the Fraunhofer 
lines. A few of the most prominent of these lines are shown 
in Fig. 80, with the letters of the alphabet by which they are 
designated. These lines, like the bright lines of the elements, 
correspond in every case to a definite degree of refrangibility, 
and therefore have a fixed position on the scale of the spectro- 
scope. Moreover, what is very remarkable, the bright and 
the dark lines have in several cases absolutely the same 
position. 

It is easy to construct the spectroscope so that the two halves 
of the slit may be illuminated from different sources. If then 
we admit a beam of sunlight through one half, and the light 
of a sodium flame through the other half, we shall have the 
two spectra super-imposed in the same field, as in Fig. 91, 



Fig. 91. 




and it will be seen that the two parts of the sodium band, 
which appears as a double line under a high power, coincide 
absolutely in position with the double dark line D in the 
solar spectrum. But a still more striking coincidence has 
been observed in the case of iron, for the eighty well-marked 
bright lines in the spectrum of this metal correspond absolutely 
both in position and in strength with eighty of the dark lines 
of the solar spectrum. Now, the chances that such coinci- 
dences are the result of accident, are not one in one billion 
billion ; and we are therefore compelled to believe that the 
two phenomena must be connected. A simple experiment 
shows what the relation probably is. 

If we place before the spectroscope a sodium flame, we see, 
of course, the familiar double line. If now we place behind 



186 RELATIONS OF THE ATOMS TO LIGHT. 

the sodium flame a candle flame, so that the candle also shines 
into the slit, but only through the sodium flame, we shall see 
the same bright lines projected upon the continuous spectrum 
of the candle. If, however, we put in place of the candle an 
electric light, we shall find that while the continuous spectrum 
is now far more brilliant than before, the sodium lines appear 
black. The explanation of this singular phenomenon is to be 
found in a principle, now well established both theoretically 
and experimentally, that a mass of luminous vapor, while other- 
wise transparent, powerfully absorbs rays of the same refrangi- 
bility which it emits itself* Hence, in our experiment, the 
very small portion of the spectrum covered by the sodium line 
is illuminated by the sodium flame alone, while all the rest of 
the spectrum is illuminated from the source behind, and the 
effect is merely one of contrast, the sodium lines appearing 
light or dark according as they are brighter or darker than the 
contiguous portions of the spectrum. 

In a similar way the bright lines of a few other elements 
have been inverted, and these experiments would lead us to 
infer that the Fraunhofer lines themselves are formed by a 
brilliant photosphere shining through a mass of less luminous 
gas. In other words, it would appear that the sun's luminous 
orb is surrounded by an immense atmosphere which intercepts 
a portion of his rays, and that we see as dark lines what would 
probably appear as bright bands, could we examine the light 
from the atmosphere alone. 

If then our generalization is safe, the dark and the bright 
lines are the same phenomena seen under a different aspect, 
and the one as well as the other may be used to identify the 
different chemical elements. Hence, then, there must be both 
iron and sodium in the sun's atmosphere, and for the same 
reason we conclude that our luminary must contain Hydrogen, 
Calcium, Magnesium, Nickel, Chromium, Barium, Copper, and 
Zinc, while there is equally good evidence that Gold, Silver, Mer- 
cury, Cadmium, Tin, Lead, Antimony, Arsenic, Strontium, and 
Lithium are not present, at least in large quantities. It is, 
moreover, worthy of notice that the lines neither of oxygen, 
nitrogen, nor indeed of any of that class of bodies formerly 
called metalloids, have been recognized in the solar spectrum ; 
but then the spectra of these elements, so abundant on the 



RELATIONS OF THE ATOMS TO LIGHT. 187 

earth's surface, 'are so much feebler than those of the metals, 
that it is doubtful whether the negative evidence of the spec- 
troscope is trustworthy in these cases. 

The elements thus recognized in the sun only account for a 
small portion of the dark lines, and the scheme of the chemical 
elements is apparently so incomplete on the earth, at least so 
far as we know it (103), that we should not be surprised to 
find a multitude of new forms of elementary matter at the cen- 
tre of the solar system. But, on the other hand, the meteorites 
have brought to us no new elements, and their evidence, there- 
fore, as far as it goes, is adverse to the assumption that there 
exists in the sun's atmosphere such a great number of unknown 
elements as the dark lines would indicate, and this obvious ex- 
planation of their vast number cannot be regarded as probable. 

If next we turn the spectroscope on some of the brighter 
fixed stars, we shall see continuous spectra like the solar 
spectrum, of greater or less extent, and covered by dark lines. 
A careful comparison of these lines would seem to indicate 
that the stars differ very greatly from each other, although in 
general they are bodies similar to our sun; and if our theory 
is correct, we have been able to detect the presence of sodium, 
magnesium, hydrogen, calcium, iron, bismuth, tellurium, 
antimony, and mercury in Aldebaran, and other elements in 
other stars. 

The most remarkable result of stellar chemistry remains yet 
to be noticed. On examining the nebulae with the spectro- 
scope, it has been found that while some of them show a con- 
tinuous spectrum, there are a number of these remarkable 
bodies which exhibit the phenomena of bright lines. This 
would lead us to the conclusion that the last are really, as the 
nebular theory assumes, masses of incandescent gas, while the 
first are not true nebulae, but simply clusters of very distant 
stars. An examination of the comets has confirmed the pre- 
vious conclusion that they also are mere masses of gas, but, 
singularly enough, the light from the coma of one of those 
bodies gave a continuous spectrum, due .probably to reflected 
sunlight. 

98. Absorption Spectra. — When a luminous flame is viewed 
with a spectroscope through a solution of any salt of the 
metal Erbium, the otherwise continuous spectrum of the flame 



188 RELATIONS OF THE ATOMS TO LIGHT. 

is seen to be interrupted by several broad bands, which have a 
definite position, and are a valuable means of recognizing the 
presence of this very rare element. This absorption spectrum, 
as it is called, is simply the reverse, the "negative" of the 
luminous spectrum of the same element. 

In like manner the salts of Didymium give an equally 
characteristic, although very different, absorption spectrum, 
which is in fact the only sure test we possess for this remark- 
able elementary substance ; and as the bands may under some 
conditions be seen with reflected, as well as with transmitted 
light, we may apply the test even to opaque solids. Also, the 
same absorption bands are obtained either when the light is 
transmitted through a liquid solution, or through a solid crystal 
of cm?/ salt of the metal ; and, moreover, the incandescent vapor 
of the metal shows bright bands corresponding to the dark 
bands in position. These facts would seem to show that the 
characteristic spectrum bands of an element may be, at least 
to some extent, independent both of the state of aggregation, 
and of the condition of combination of the elementary atoms. 

Many substances besides the compounds of the elements 
just noticed, give characteristic absorption spectra which have 
been found to be useful chemical tests, especially in the case 
of blood, and certain other bodies of organic origin. The 
most remarkable phenomena of this class are the absorption 
spectra which are seen when a luminous flame is viewed with 
a spectroscope through various colored vapors, such as those 
of nitric per-oxide, bromine, and iodine. The dark bands are 
then very numerous, and in some cases may be resolved into 
well-defined lines. Indeed, the absorption bands are a class of 
phenomena clo-ely allied to the Fraunhofer lines, many of 
which are known to result from the absorption by the earth's 
atmosphere of solar rays of certain degrees of refrangibility : 
and all these facts, with many others, prove that gases and 
vapors may exert their peculiar power of elective absorption 
at the ordinary temperature, as well as when incandescent. 
As a general rule, however, the absorption bands are not, like 
the bright lines of the metallic spectra or their representatives 
among the dark lines of the solar spectrum, definite images of 
the slit, but they are darker portions of the spectrum more or 
less regularly shaded, and correspond to the broad bands or 



RELATIONS OF THE ATOMS TO LIGHT. 189 

luminous spaces in the spectra of the metallic vapors when 
not intensely heated. In each case the effect results from the 
blending of a greater or less number of images of the slit, 
differing in relative position and intensity. 

99. Theory of Exchanges. — The facts of the two last 
sections are all illustrations of a general principle already 
referred to in connection with the reversal of the sodium 
spectrum. This principle is known as the " Theory of Ex- 
changes," and has been stated as follows : " The relation 
between the power of emission, and power of absorption 
for each hind of rays (light or heat) is the same for all 
bodies at the same temperature." . . . . " Let R denote the 
intensity of radiation of a particle for a given description of 
light at a given temperature, and let A denote the proportion 
of rays of this description incident on the particle which it 
absorbs; then R-r-A has the same value for all bodies at the 
same temperature, — that is to say, this quotient is a function 
of the temperature only." 

The law of exchanges finds its widest application in the 
phenomena of radiant heat, and so far as experiments have 
been made, it appears to be true in its greatest generality. In 
applying it to explain the reversal of the spectra of colored 
flames, we have only to deal with a single body in its relations 
to rays of different qualities. If the principle is true, the 
absorbing power of such a body at a given temperature must 
bear a fixed ratio to its power of emission for each kind of 
ray. If, for example, it has a great power of emitting certain 
rays of red light, it has a proportionally great power of 
absorbing the same rays. If, again, it has a feeble power of 
emitting violet rays of definite quality, its power of absorbing 
such rays is proportionally feeble, and bears the same ratio to 
the power of emission as before ; and, lastly, it has no power 
of absorption over such rays as it does not itself emit. More- 
over, it would follow that, although the relation of the absorb- 
ing to the radiating power might vary very greatly, so that, 
as the temperature falls, the last may become inconsiderable 
as compared with the first, or even vanish, no essential change 
in the character of the elective absorption would be thus in- 
duced. Hence, we should expect that bodies would absorb 
when cold rays of the same quality which they emit when hot, 



190 RELATIONS OF THE ATOMS TO LIGHT 

and also that opaque solids when heated would emit" white 
light. We have seen that the general order of the phenomena 
is that which the law of exchanges would predict, and here, for 
the present, our knowledge stops. We have as yet been able 
to form no satisfactory theory in regard to the relations of the 
molecular structure of bodies to the medium through which the 
waves of light or heat are transmitted. It is, however, 
worthy of notice that Euler, one of the earliest and ablest 
investigators of undulatory motion, predicted the discovery of 
the law of exchanges, in a>suming as a fundamental principle of 
the undulatory theory that a body can only absorb oscillations 
isochronous with those of which it is itself susceptible. 

100. General Conclusions. — The facts that have been 
stated in this chapter are suffich-nt to show, that, although yet 
in its infancy, spectrum analysis promises to be one of the 
most powerful instruments of investigation ever applied in 
physical science. It seems to be the key which will in time 
open to our view the molecular structure of matter ; and even 
now the results actually obtained suggest speculations in 
regard to the ultimate constitution of matter, of the most 
interesting character. The several monochromatic rays which 
the atoms of the elements emit, must receive their peculiar 
character from some motion in the atoms themselves which is 
isochronous with the motion they impart. Is it not then in 
this motion that the individuality of the element resides, and 
may not all matter be alike in its ultimate essence? Such 
speculations, however wild, are not wholly unprofitable, if only 
they stimulate investigation and thus lead to further dis- 
coveries. 




CHAPTER XVII. 

CHEMICAL CLASSIFICATION. 

101. General Principles. — The glimpses that we have been 
able to gain of the order in the constitution of matter give us 
grounds for believing that there is a unity of plan pervading 
the whole scheme, and encourage a confident expectation that 
hereafter, when our knowledge becomes more complete, chem- 
ists may attain to at least such a partial conception of this 
plan as will enable them to classify their compounds under 
some natural system ; and in imagination we may even look 
forward to the time when science will be able to express all 
the possibilities of this scheme with a few general formulae, 
which will enable the chemist to predict with absolute cer- 
tainty the qualities and relations of any given combination of 
materials or conditions. But although to a very slight extent 
the idea has been realized for a small class of the compounds 
of carbon, yet as a whole this grand conception is as yet but a 
dream. The more advanced student will find that in limited 
portions of some few fields of investigation a fragmentary clas- 
sification is possible, as in mineralogy; but, when he attempts 
to comprehend the whole domain, he becomes painfully aware 
of the immense deficiencies of his knowledge ; he is confused 
by the numerous chains of relationship, which he follows, with 
no result, to sudden breaks, and soon becomes convinced that 
all such efforts must be fruitless until more of the missing links 
are supplied. 

The best that can now be done in an elementary treatise on 
chemistry is to group together the elements, or, rather, the 
elementary atoms, in such families as will best show their 
natural affinities ; and then to study, under the head of each 
element, the more important and characteristic of its com- 
pounds. However little value such a classification may have 
in its scientific aspect, it will bring together, to a greater or less 
extent, the allied facts of the science, and thus will help the 
mind to retain them in the memory. 



192 CHEMICAL CLASSIFICATION. 

In classifying the elementary atoms, the three most impor- 
tant characters to be observed are the Prevailing Quanti valence, 
the Electrical Affinities, and the Crystalline Relations. The 
first of these characters serves more particularly to classify the 
elements in groups, the second to determine their position in 
the groups, and the last to control the indications of the other 
two. 

The crystalline relations of the atoms can only be deter- 
mined by comparing the crystalline forms of allied compounds, 
and involve the principles of isomorphism already discussed. 
Moreover, in order to reach the most satisfactory scheme of 
classification, we must take into consideration other properties 
of these compounds besides the crystalline form ; which, al- 
though they may not be so precisely formulated, are frequently 
important aids in forming correct opinions as to the relations of 
the atoms. It will also be evident, from what has previously 
been stated, that more trustworthy inferences as to these rela- 
tions may frequently be drawn from the crystalline form and 
properties of allied compounds than from those of the element- 
ary substances themselves ; for, in addition to the fact that so 
many of these substances crystallize in the isometric system, 
whose dimensions admit of no variation, it is also true that, in 
our ignorance of the molecular constitution of most of them, we 
often have more certainty, in the case of compounds, that our 
comparisons are made under identical molecular conditions. 

102. Metallic and Non- Metallic Elements. — In all works on 
chemistry since the time of Lavoisier, the elementary sub- 
stances have been divided into two great classes, — the metals 
and the non-metals ; and the distinction is undoubtedly funda- 
mental, although too much importance has been frequently 
attached to the accident of a brilliant lustre. The character- 
istic qualities of a metal, with which every one is more or less 
familiar, are the so-called metallic lustre, that peculiar adapt- 
ability of molecular structure known as malleability or ductility, 
and the power of conducting electricity or heat. These qualities 
are found united and in their perfection only in the true metals, 
although one or even two of them are well developed in several 
elementary substances which, on account of their chemical 
qualities, are now almost invariably classed with the non- 
metals, — as, for example, in selenium, tellurium, arsenic, 



CHEMICAL CLASSIFICATION. 193 

antimony, boron, and silicon. Besides the properties above 
named, many persons also associate with the idea of a metal a 
high specific gravity ; but this property, though common to most 
of the useful metals, is by no means universal ; and, among the 
metals with which the chemist is familiar, we find the lightest, 
as well as the heaviest, of solids. The non-metallic elements, 
as the name denotes, are distinguished by the absence of metal- 
lic qualities ; but the one class merges into the other. 

The presence or absence of metallic qualities in the ele- 
mentary substances is for some unknown reason intimately 
associated with the electrical relations of their atoms, — those of 
the metals being electro-positive, while those of the non- 
metals are electro-negative, with reference, in each case, to the 
atoms of the opposite class. In the classification given in 
Table II. we have associated together in the same family both 
the metals and the non-metals having the same quanti valence, 
believing that such an arrangement not only best exhibits the 
relations of the atoms, but also that in a course of elementary 
instruction it presents the facts of chemistry in the most logical 
order. 

103. Sckrme of Classification. — The classification of the 
elementary atoms which has been adopted in this book is shown 
in Table II. 

In the first place the atoms are divided into two large 
families, the Perissads and the Artiads (27). 

Secondly, these families are subdivided into groups (separated 
by bars in the table) of closely allied elements. The atoms of any 
one of these groups are isomorphous ; and they are arranged 
in the order of their weights, which is found to correspond also, 
in almost every case, to their electrical relations. Each group 
forms a very limited chemical series ; and not only the weights 
and the electrical relations of the atoms, but also many of the 
physical qualities of the elementary sub-tances, vary regularly 
as we pass from one end of the series to the other. The order 
of the variat'on, however, is not always the same ; for while in 
some cases the lightest atoms of a series are the most electro- 
negative, in other cases they are the mo-t electro-positive. 

Thirdly, in arranging the groups of allied atoms we have 
followed the prevailing quantivalence of the group, and those 
groups whose elementary atoms exhibit in general the lowest 



194 CHEMICAL CLASSIFICATION. 

quantivalence are, as a rule, placed first in order ; but with 
our present limited knowledge there must be some uncertainty 
in regard to the details of such an arrangement, and the prin- 
ciple has sometimes been violated so as to bring together those 
groups of atoms which are most allied in their chemical rela- 
tions. 

The remarks already made in regard to the general scheme 
of chemical classification apply with almost equal force to the 
partial system here attempted. The very attempt makes evi- 
dent the fragmentary character of our knowledge, even in re- 
gard to the exceedingly limited portion of the subject with 
which we are dealing. The idea of classification by series was 
first developed in the study of organic chemistry, where the 
principle is much more conspicuous than among inorganic com- 
pounds. Thus, as lias been shown (40), we are acquainted 
with twenty acids resembling acetic acid, which form a series 
beginning with formic acid and ending with meliss'c acid. Each 
member of this series differs in composition from the preceding 
member by CH 2 , or by some multiple of this symbol ; and the 
properties of the compounds vary regularly between the extreme 
limits, according to well-established laws. Moreover, many 
other similar, although more limited, series of compounds are 
known, and the principle realized in these organic series seems 
to be the true idea of all chemical classification. But, in attempt- 
ing to apply it to the chemical elements, we find only two or three 
groups of atoms where the series is of sufficient extent to make 
the relations of the members evident. In most cases it would 
seem as if we only knew one or two members of a series, and 
this apparent ignorance not only throws doubt on the general 
application of our principle, but also renders uncertain the details 
of our scheme, even a-suming that the principle of the classi- 
fication is correct* Hence, also, great differences of opinion 
may be reasonably entertained in regard to the position which 
the different atoms ought to occupy in such a scheme. 

Another very important cause of uncertainty in any scheme 
of classifying ihe elements arises from the double relationships 
which many of them manifest. Thus iron, which we have 
associated with manganese and aluminum, is in some of its 
relations clo-ely allied to magnesium and zinc. Many other 
elements resemble iron in having a similar two-fold character, 



CHEMICAL CLASSIFICATION. 195 

and different authors may reasonably assign to such elements 
different places in their systems of classification, according as 
they chiefly view them from one or the other aspect. Hence 
arises a degree of uncertainty which affects our whole system, 
and cannot be avoided in the present state of the science. 

Indeed, no classification in independent groups can satisfy 
the complex relations of the elements. These relations cannot 
be represented by a simple system of parallel series, but only 
by a web of crossing lines, in which the same element may 
be represented as a member of two or more series at once, 
and as affiliating in different directions with very different 
classes of elements. In the present fragmentary state of our 
knowledge, such a classification as we have just indicated is 
not attainable. The scheme adopted in this book only indi- 
cates in each case a single line of relationship ; but we have 
always endeavored to place each element in that relation 
which is the most characteristic ; and, however imperfect such 
a scheme may be, it will nevertheless assist study by bringing 
before the student's mind the facts of the science in a syste- 
matic and natural order. 

104. Relations of the Atomic Weights. — If the principle of 
classification which we have adopted is correct, and the ele- 
ments actually belong to series like those of the compounds of 
organic chemistry, we should naturally expect that the atomic 
weights would conform to the same serial law ; and it is a re- 
markable fact that the differences between the atomic weights 
of the elements of the same group are in most cases very nearly 
multiples of 16. The value of this common difference varies 
between 15 and 17, and we must admit in some cases the 
simplest fractional multiples ; but the mean value is very 
nearly 1 6, and the frequent occurrence of this difference is 
very striking. This numerical relation is not absolutely exact, 
but here, as in the periods of the planets, in the distribution of 
leaves on the stem of a plant, and in other similar natural 
phenomena, there is a marked tendency towards a certain nu- 
merical result, which is fully realized, however, only in com- 
paratively few cases. 

Other numerical relations which have been noticed between 
the atomic weights are probably only phases of the same law 
of distribution in series. Thus the atomic weight of sodium is 



196 CHEMICAL CLASSIFICATION. 

very nearly the mean between that of lithium and potassium ; 
and the atomic weights of chlorine, bromine, and iodine, of glu- 
cinum, yttrium and erbium, of calcium, strontium, and barium, 
of oxygen, sulphur, and selenium, are similarly related. Again, 
there are several pairs of allied elements, between whose 
atomic weights there is very nearly the same difference. Thus 
the difference between the atomic weights of indium and cad- 
mium is very nearly the same as that between the atomic 
weights of magnesium and zinc, and the difference between the 
atomic weights of niobium and tantalum the same as that be- 
tween the atomic weights of molybdenum and tungsten. A 
careful study of the atomic weights will also reveal many other 
approximate relations of the same sort ; but although the 
study of these relations is highly interesting, and may lead here- 
after to valuable results, yet no great importance can be at- 
tached to them in the present state of the science. 



PART II. 



INTRODUCTION 



Having developed in Part I. the fundamental principles of 
chemical science, we shall next give, in Part II., a brief sum- 
mary of the more important elements and compounds, exhib- 
iting their constitution and relations by means of formulae and 
reactions, and adding a number of questions and problems, 
which will serve to direct the attention of the student to the 
more important facts and principles, or to those which, being 
only implied in the context, might be otherwise overlooked, 
and which will also give him the means of testing the thor- 
oughness and accuracy of his knowledge. The answers to the 
problems have been calculated with the four-place logarithms, 
which will be found at the end of the volume. Used in con- 
nection with the table of antilogarithms which accompanies 
them, the logarithms give results which are accurate to the 
fourth significant figure, and this degree of accuracy exceeds 
in almost every case that of the experimental data given in 
the problems. With certain exceptions referred to below, the 
answers to the questions are either stated or implied in the 
immediate context, or in the sections and formulae to which 
reference is made. The references to sections are enclosed in 
parentheses, and those to formulae in brackets. Direct ques- 
tions on the facts stated in the summary are seldom given, and 
obviously would be superfluous ; but the student should make 
himself thoroughly acquainted with the subject-matter of each 
section before he attempts to answer the questions or solve the 
problems which follow. In studying the book, however, he 
should aim to acquire a knowledge of the general principles 
and mutual relations which are exhibited, rather than to com- 
mit to memory the isolated facts. He must never forget that 
he is dealing, not with abstractions, but with real things and 
actual phenomena, and that chemical formulae are merely ex- 



200 INTRODUCTION. 

pressions of definite facts ascertained by experiment. More- 
over, he mu*t discriminate with the greatest care between the 
facts directly stated or expressed by the reactions, and the in- 
ferences drawn from them, and he should be required to state 
clearly the successive steps in every process of inductive rea- 
soning. As was stated in the preface, this portion of the book 
is only intended as an auxiliary to lecture-room or laboratory 
instruction, and the closer the lessons can be connected with 
the experimental illustrations the better. 

The elements are studied in the following chapters in the 
order in which they are arranged in Table II., and in connec- 
tion with each element we describe, or at least mention, the 
more important compounds which it forms with the elements 
preceding it in our classification. At least this is the general 
rule, but, so far as regards the compounds, we do not follow 
this order invariably, departing from it whenever it may be 
necessary to illustrate the relations of the element we may be 
studying. Thus we describe with each element its chief oxy- 
gen and sulphur compounds from the first. No attempt has 
been made to embrace the whole field, but the aim has been to 
illustrate fully the principles of chemical philosophy, and to 
give a clear idea of that phase of the scheme of nature which 
has been revealed by the study of chemistry. As stated in the 
Preface, the ''Questions and Problems" are an essential feature 
in the plan of the work, and serve to supplement as well as to 
illustrate the text. The student will find that the knowledge 
which he gains inferentially, while seeking the answers to the 
questions or solving the problems, is peculiarly valuable, and 
the acquisition has something of the zest of new discovery. As 
he advances, he will meet with questions which he cannot fully 
answer without consulting more extended works, and which are 
intended to direct his study beyond the limits of this book. He 
may consult in such cases Watts's Dictionary of Chemistry, 
Miller's Elements of Chemistry, Percy's Metallurgy, and Dana's 
System of Mineralogy. 



CHAPTER XVIII. 

THE PERISSAD ELEMENTS. 
Division I. 

105. HYDROGEN. ff= 1. — Monad. The lightest 
atom, and the standard of quanti valence. Very widely diffused 
in nature. Forms one ninth of water, and is a constituent of 
almost all vegetable and animal sub.-tances as well as of many 
minerals. The essential constituent of all acids and bases, from 
which it is readily displaced by other atoms. 

106. Hydrogen Gas. H~H. — The lightest substance known 
in nature. Sp. Gr. = 1, the standard of comparison. Seldom 
found in a free state in nature. Best prepared by the action of 
zinc or iron on dilute sulphuric acid. 

Xn + (# 2 S0 4 + Aq) = (ZaSO, + Aq) + SHU. [64] 

Very combustible. Has the greatest calorific power of any 
substance known. Aqueous vapor sole product of its com- 
bustion. 

2 SHU + ®=® = 23H 2 ®. [65] 

107. Hydric Oxide (Water). ff 2 0. — The universally dif- 
fused liquid of the globe. The life-blood of nature, and the 
chief constituent of organized beings. Below 0° a crystalline 
solid (hexagonal system, Figs. 14 and 16). Sp. Gr. = 0.918. 
Under the ordinary pressure of the air it boils at 100°, but 
exists in the atmosphere in the state of vapor, at all temper- 
atures. For maximum tension of vapor at different temper- 
atures see Chem. Phys. (284 and 312). Water is an almost 
universal solvent and the medium of most chemical changes. 
Its molecular structure is regarded as the type of a very 
large class of chemical compounds. Its composition may be 
determined, — First, by electrolysis (91 and [65] reversed). 

9* 



202 HYDROGEN. [§108. 

Secondly, by passing a mixture of steam and chlorine gas 
through a red-hot tube. 

2IH 2 ® + 2@1-@1 = 4HI01 + ®=®. [66] 

Thirdly, by exploding in an eudiometer-tube a mixture of oxy- 
gen and hydrogen gas [65], Fourthly, by parsing hydrogen 
gas over heated cupric oxide. 

CllO + EMU = Cu + S3 2 ®. [67] 

Water combines with anhydrides to form acids, as 



SOs + H 2 = Hr0 2 =S0 2 , 
P 2 5 + 3H 2 = 2H^O f PO 



[68] 



It combines with metallic oxides to form hydrates, bases, or 
alkalies, as 

Na,0 + K A = 2Na-0-H or CaO + H 2 = Ca=0./H 2 . [69] 

It combines with many salts as water of crystallization, as 

Fe-S0 4 . 1H 2 Cryst. Ferrous Sulphate. 

108. Hydroxyl. HO. — An important compound radical, 
which may be regarded as a factor (28) in the molecules of 
many chemical compounds, and for this reason it is sometimes 
convenient to write its symbol Ho (22). The oxygen bases 
may be considered as compounds of hydroxyl with electro-posi- 
tive atoms or radicals, and the oxygen acids as compounds of 
the same with electro-negative atoms or radicals. Thus we 
may write the symbols of the following compounds as shown 
below : — 

Sodic Hydrate Na-0~H or JUa-Ho, 
Banc Hydrate Ba=0 2 =H 2 " Ba=Ho 2 , 

Ferric Hydrate [i^ 2 ]10 fa l# 6 « \_Fe 2 JHo & , 



Nitric Acid HO-N0 2 « Ho-N0 2 , 

Sulphuric Acid H 2 =0 2 =S0 2 " -HofSO* 
Phosphoric Acid HfO^PO " Ho^PO. 



[70] 



109. Hydric Peroxide ( Oxygenated Water) . H 2 2 or Ho -Ho, 



§ 109.] QUESTIONS AND PROBLEMS. 203 

— Best regarded as the "radical substance" (22 and 69) 
corresponding to hydroxyl. In its most concentrated form it is 
a colorless liquid of the consistency of syrup, and having a de- 
cided odor resembling chlorine. Soluble in water in all pro- 
portions. Prepared by action of carbonic acid on baric peroxide. 

KstO i +(ff i C0 8 + Aq) = BaCO s + (B 2 2 + Aq). [71] 

Carbonic anhydride is passed through water in which Ba0 2 is 
suspended and the solution of B 2 2 subsequently evaporated in 
vacuo. Decomposed by fine metallic powders, and also spon- 
taneously at temperatures higher than 22°, into water and oxy- 
gen gas. 

(2B 2 2 + Aq) = (2B 2 + Aq) + ®=®. [72] 
It liberates iodine from its compounds. 

2KI+ (Bo-Bo + Aq) = II + (2K-Bo + Aq). [73] 
It generally acts as an oxidizing agent. 

¥h&+(iB 2 2 + Aq) = Vh$O 4 + (4B 2 + Aq). [74] 
It sometimes, however, acts as a reducing agent. 
A»O + (J5&O,+J0=Ag, + (f&0+^) + ®<B. [75] 



Questions and Problems. 1 

1. What distinction can be drawn between a chemical element 
and an elementary substance, it being understood that the word ele- 
ment is used in a restricted sense, as applying only to the ultimate 
atoms into which matter may be resolved ? Illustrate the distinction 
by the case of hydrogen. (69 ; 18 and 22.) 

2. What is the essential characteristic of an acid and of a base ? 
(35 and 36.) 

3. What is the ground for the belief that each molecule of hydro- 
gen gas consists of two atoms ? (19-) 

1 It is assumed in all the problems of this book that the temperature is 
0° C, and the pressure 76 c. m., unless otherwise stated. The following 
abbreviations will be used: c. m., centimetre; <T~ 5T 3 , cubic centimetre; 
d. m. 3 , cubic decimetre; kilo., kilogrammes, &c. (See Table I.) 



204 QUESTIONS AND PROBLEMS. 

4. The litre and the crith, the molecular weight of hydrogen and 
its molecular volume, sustain what relation to each other? btate the 
reason far the rule on page 49. (2 and 25.) 

5. How many grammes of zinc and how many of sulphuric acid 
will yield one litre of hydrogen gas? 

Ans. 2.92 grammes of zinc, and 4.39 grammes of sulphuric acid. 

G. If 45 grammes of zinc are used in reaction [64], how many 
cubic centimetres of sulphuric acid must be used also, and how many 
grammes of zincic sulphate, and how many litres of hydrogen gas, 
will be formed in the process (Sp. Gr. of H 2 SO^ = 1.843) ? 

Ans. 36.7 c. m. 3 of sulphuric acid, 111.3 grammes of zincic sul- 
phate, and 15.4 litres of hydrogen. 

7. What volume of water should be mixed with the s^phuric acid 
in the last problem, assuming that the reaction takes pLce at 20°, 
and that 100 parts of water at that temperature will dissolve 53 
parts of zincic sulphate? 

Ans. 209.9 c. in. 3 , or enough to dissolve all the zinc salt formed. 

8. What weight of iron must be used to generate sufficient hydro- 
gen to raise in the atmosphere by its buoyancy a total weight of 121 
grammes (Sp. Gr. of air 14.5 nearly) ? 

Ans. 100 litres of hydrogen gas will be required, and this can be 
made from 250.9 grammes of iron. 

9. Assuming that the principle of (17) is correct, why does it fol- 
low from reaction [65] that the molecule of oxygen gas must contain 
at least two atoms ? 

10. What is the volume of 4.480 grammes of hydrogen at 273°.2 
[ 9 ]? Ans. 100 litres. 

11. What is the volume of 4.480 grammes of hydrogen at 0° and 
under a pressure of 38 c. m. [4] ? *Ans. 100 litres. 

12. A block of ice weighs 36.72 kilos. What is its volume [1] ? 

Ans. 40 (Lin? 

13. An iceberg is floating in sea water (Sp. Gr. = 1.028). What 
proportion of its bulk is submerged ? Ans. 0.8932. 

14. One kilogramme of steam at 100° will melt how many kilos. 
of ice ? 

Ans. The steam by condensing and cooling would give out 637 
units of heat, which is adequate to melt 637 ~ 79 = 8 + 
kilogrammes of ice. (14 and 16.) 

15. "What is the weight of one litre of confined steam at the tem- 
perature of 144° ? Tension of steam at 144° equals 4 atmospheres. 

Ans. Weight of litre of steam at 0° and 76 c. m. would be theo- 
retically 9 criths. Hence weight at 144° and 4 X 76 c. m. 
is, by [6] and [10], 23.58 criths or 2.113 grammes. 



QUESTIONS AND PROBLEMS. 205 

16. What is the weight of one litre of superheated steam under 
normal pressure, and at 546°.4 ? Ans. 0.2688 grammes. 

1 7. Water is forced into a glass globe containing dry air, at the 
temperature of 10u° C. and under the uormal pressure, as long as it 
continues to evaporate. What will be the tension of the moist air? 

Ans. Water or any other liquid evaporates into a confined space 
until the vapor attains its maximum tension for the existing 
temperature, even when the space is filled with another gas ; 
and the tension of the mixture of gas and vapor is equal to 
the sum of the tension which each would exert sep irately. 
Chem. Phys. (312). The maximum tension of aqueous 
vapor at 100° is 76 c. m., and hence the tension of the moist 
air in the globe must be 152 c. m. 

18. A volume of hydrogen gas standing in a bell-glass over a 
pneumatic trough, and consequently saturated with moisture, meas- 
ures 100 c~in. 3 . The temperature is 22°. 3 and pressure on the gas 
76 c. m. What would be the volume under the same conditions if 
the air were perfectly dry ? 

Ans. The maximum tension of aqueous vapor at given temper- 
ature is 2 c. m. Hence if vapur were removed, the tension 
of the gas would become 74 c. m., provided the volume re- 
mained constant. But the exterior pressure being 76 c. m., 
the volume must accommodate itself to this condition, and 
hence by [4] would be reduced to 97.36 c. m. 

19. What is the Sp. Gr. of aqueous vapor? What is meant by 
the term Sp. Gr. as applied to a vapor, and under what conditions is 
it assumed to be taken ? (1 and 17.) Ans. 9. 

20. In Table ITT. the weight of one litre of aqueous vapor under 
the standard conditions of temperature and pressure is given as 9 
criths. Why is this value a fiction ? and why is an impossible value 
given in the table ? Chem. Phys. (329). 

21. In the experiment indicated by reaction [66] the oxygen gas 
was collected in a bell-glass over water. It measured 1,101 c. m. 8 
at the temperature 22°. 3 and under a pressure of 76 c. m. What 
was the volume of chlorine gas used, meamred under the normal 
conditions ? The tension of aqueous vapor at 22°.3 is 2 c. m. 

Ans. 2 litres. 

22. How much copper will be reduced in the formation of nine 
grammes of water, and what volume of hydrogen gas will be used in 
the reaction ? 

Ans. 31.7 grammes of copper and 11.16 litres of hydrogen. 

23. It has been found by exact experiments that for every nine 



206 QUESTIONS AND PROBLEMS. 

grammes of water formed by reaction [67] the cupric oxide lost in 
weight eight grammes. What is the percentage composition of 
water? Ans. 11.112 of hydrogen and 88.888 of oxygen. 

24. Given percentage composition of water and the Sp. Gr. of 
aqueous vapor, and assuming that the molecule of water contains 
only one oxygen atom, how can you deduce the atomic weight of 
oxygen? (23.) 

25. Assuming that all the heat of combustion is utilized, how 
many litres of hydrogen must be bu* nt to convert into free steam 
one kilogramme of boiling water, and how does the volume of steam 
generated compare with the volume of gas burnt ? 

Ans. 176.8 litres of hydrogen gas and 1,240 litres of steam, when 
reduced to standard conditions. (14 and 17.) (61.) 

26. Assuming that all the heat of combustion is retained in the 
aqueous vapor formed from the burnt hydrogen, how will the vol- 
ume of the expanded vapor compare with that of the gas consumed ? 

Ans. By problem on page 121 it appears that the temperature of 
the vapor would be, under the conditions assumed, 6,853°. 
Hence the volume would be 26.08 times as great as that of 
the gas [9]. 

27. Assuming that the whole volume of gas resulting from the 
electrolysis of water is retained in the space previously occupied by 
the waier, what would be its tension ? Ans. 1,860 atmospheres. 

28. What is the relation of an anhydride to an acid, or of a me- 
tallic oxide to a hydrate ? (37 and 47.) 

29. What objections may be raised to the method of writing the 
symbols of acids and bases used in [70] ? 

30. What is the distinction between a compound radical and a 
radical substance ? 

31. Why does reaction [73] sustain the view that hydric perox- 
ide contains the radical hydroxyl ? Do not reactions [72], [74], 
and [75] point to another view of its constitution? 

32. Analyze reaction [75], and show that it is in harmony with 
the modern theory of the constitut.on of the oxvgen molecule. 



§113.] FLUORINE. — CHLORINE. 207 



Division II. 

110. FLUOHINE. ^=19. — Quanti valence usually one, 
but its atomicity is probably of higher order. A chief constit- 
uent of fluor-spar, CaF 2 . and of cryolite, Na 6 Al 2 F 12 . Found also, 
but in small quantities, in Apatite, Tourmaline, Mica, and a few 
other minerals. Also in the bones of animals, especially in the 
teeth. The elementary substance F~F is undoubtedly a gas, 
but it has not with certainty been isolated. 

111. Hydrofluoric Acid. HF. — The anhydrous acid is at 
15° a colorless mobile liquid, extremely volatile, boiling at 19.5°, 
densely fuming in the air, and attracting greedily water from 
the atmosphere. It is exceedingly corrosive, and a highly dan- 
gerous substance. The dilute acid is obtained by distilling a 
mixture of powdered fluor-spar and sulphuric acid in a plati- 
num or lead retort. 

CaF 2 + (ITjSOi + Aq) = CaS0 4 + 2 HEP + ^q. [76] 

Cryolite may be used advantageously instead of fluor-spar. 
This acid is distinguished for its power of dissolving silica, with 
which it forms volatile products. Hence it is much u^ed in 
chemical analysis for decomposing siliceous minerals, and in the 
arts for etching glass. 

112. CHLORINE. 01=35.5. — Quantivalence usually one, 
but atomicity probably of a higher order. Very widely dis- 
tributed in nature, chiefly in combination with sodium, forming 
common salt. 

113. Chlorine Gas. CI- CI. — Yellowish-green gas, which 
may be liquefied by pressure, but has never been frozen. Sol- 
uble in water, with which it forms at 0° a crystalline hydrate. 
Highly corrosive, and enters into direct union with most of the 
elementary substances. Discharges vegetable colors and de- 
stroys noxious effluvias, and hence much used in the arts as a 
bleaching and disinfecting agent. Best prepared by gently 
heating in a glass flask a mixture of hydrochloric acid and man- 
ganic dioxide. 

MnO, + (±HCl + Aq) = 

{MnCl, + 2R 2 + Aq) + Cgl-Ol. [77] 

Chlorine gas is a very important chemical reagent. It not 



208 



CHLORINE. 



[§ H4. 



only converts many simple chlorides into perchlorides, but, with 
the intervention of water or of some other oxygen compound, 
it also acts as an oxidizing agent, and to this effect its bleaching 
power is probably in great measure owing. 

(Sn Cl 2 + Cl 2 + Jq) = (Sn CI, + Aq). [78] 

3Co=(HO) 2 + (Cl-Cl + Ag) = 

[Co 2 ]l(HO) 6 +(Cba 2 + ^). [79] 

Chlorine has also a remarkable power of replacing hydrogen in 
many of its compounds. (31) 

114. , Hydrochloric Acid. H-Cl. — A colorless gas which 
may be liquefied by cold and pressure, but has not been frozen. 
Exceedingly soluble in water, which at 4° absorbs its own 
weight or about 480 times its volume of the gas. This solu- 
tion is very much used in the laboratory as a reagent, and an 
impure solution called muriatic acid is manufactured on a large 
scale for the uses of the arts. From the Sp. Gr. of the liquid 
acid we can determine very closely the quantity of gas held in 
solution, by means of tables in which the results of careful ex- 
perimental determinations have been tabulated. The following 
extracts from a table of Dr. Uie's give all the data required for 
calculating the problems in this book. 



Sp. Gr. 
15 3 0. 



1.2000 
1.1893 
1.1802 
1.1701 
1.1599 



Per Cent. 
HCl. 



40.777 
38.330 
36.292 
34.252 
32.213 



Sp Gr. 
15 3 C. 



1.1410 
1.1308 
1.1206 
1.1102 
1.1000 



Per Cent. 
HCl. 



28.544 
26.505 
24.466 
22426 
20.388 



Sp. Gr. 
15 J C. 



1.0899 
1.0798 
1.0697 
1.0597 
1.0497 



Per Cent. 
HCl. 



18.349 
16.310 
14.271 
1 2 233 
10.194 



Sp. Gr. 
15- C. 



1.0397 
1.0298 
1 0200 
1.0100 
1.0060 



PerCent. 
HCl. 



8.155 
6.116 
4.078 
2.039 
1.124 



Muriatic acid is prepared by heating common salt with sul- 
phuric acid in large iron retorts, and conducting the gas formed 
into large glass vessels containing water. 



<2Na CI + ff 2 S0 4 = Na 2 SO, + 25SOI. 



[80] 



When we make pure hydrochloric acid in the laboratory, we 
only use half as much salt. The gas is then given off at a 
much lower temperature, and glass retorts may be employed. 

NaCl+ (fffSOt + Aq) = (H,m-S0 4 + Aq)+mm. [81] 



§ HG.] CHLORINE. 209 

Hydrochloric acid may also be obtained by directly uniting 
hydrogen and chlorine gas. 

HI-HI + ®K9l = 2HK31. [82] 

By electrolyzing the aqueous solution, the last reaction is re- 
versed and the acid is decomposed. It may also be readily 
decomposed by metallic sodium. 

211101 + IWa ]Ya = 2]\aCl + Si-SL [83] 

Liquid hydrochloric acid dissolves most of the metals and the 
metallic oxides, and its uses in practical chemistry are illus- 
trated by the following reactions. See also [77]. 

Sn + (2HCI + Aq) — (SnCl 2 + Aq) + HI-IS. [84] 

ZllO + {2HCI + Aq) == (ZnCl 2 + H 2 + Aq). [85] 

[AIJO3+ (QHCl + Aq)= {[Al 2 ~\ C/ 6 + 3H 2 + Aq). [86] 

115. Compounds of Chlorine and Oxygen. — All of them 
unstable and most of them explosive. In regard to their mo- 
lecular constitution different views are entertained. 



Hypochlorous Anhydride 


Cl 2 


Cl-O-Cl, 


Hypochlorous Acid 


HCIO 


H-o-a, 


Chlorous Acid 


HC10 % 


H- O-O- CI, 


Chlorous Anhydride 


CW 3 


ci- 0-0-0- CI, 


Chloric Acid 


HC10 3 


H-O-OO-Cl, 


Chloric Peroxide 


Cl 2 0, 


ci-o-o-o-o-ci, 


Perchloric Acid 


HCIO, 


H-O-O-O-O-Cl. 



116. Potassic Chlorate. — The most important salt of any 
of the chlorine oxygen acids. Obtained by passing a stream 
of chlorine gas through a warm solution of caustic potash. 

(eK-0-H+ Aq) + 3Cl-Cl = 

(KC10 3 + 5KCI + Sff 2 + Aq). [87] 

Potassic chlorate, being much the less soluble, is readily freed 
from the potassic chloride by two or three crystallizations. It is 
decomposed by heat alone into potassic chloride and oxygen gas. 

2KC10 3 = 2KCI + 3 ®=®. [88] 



210 BROMINE. — IODINE. [§ 1 1 7. 

Much used for making oxygen gas, and also in fireworks and 
the preparation of detonating powder. 

117. BROMINE. Br = 80. — Quantivalence usually one, 
but atomicity probably of a higher perissad order. Associated 
with chlorine in minute quantities in saline waters and certain 
silver ores. The elementary substance (Br-Br) is a very volatile 
deep-red liquid. Sp. Gr. == 3.187. Boils at 63°. Freezes 
at 7°. 3. Prepared from the bittern of certain salt springs, by 
treating with chlorine and dissolving out the liberated bromine 
with ether. 

118. IODINE. 7=127. — Quantivalence and atomicity 
same as with bromine. Associated with chlorine in still smaller 
quantities than bromine. The elementary substance is obtained 
from the ashes of certain seaweeds. Crystalline solid ; Sp. Gr. 
= 4.95. Melts at 107°. Boils at 175°, forming a dense violet 
vapor. Very slightly soluble in water, but is readily di.-solved 
by alcohol, ether, and carbonic sulphide. Imparts to starch 
paste a deep blue color. 

The three elements, chlorine, bromine, and iodine, form a 
well-defined natural group, and a careful comparison will show 
that the properties both of the elementary substances and of 
their compounds conform closely to the law of progression which 
marks a chemical series. These elements are all highly electro- 
negative bodies, but as we descend in the series we find that 
this character becomes less marked, and hence their chemical 
energy, as manifested by the strength of their affinity for ele- 
ments of the opposite class, such as hydrogen and the electro- 
positive metals, diminishes as the atomic weight increases; 
and this law, as will appear, obtains with few exceptions in 
all the chemical series. Moreover, it will also be found, as 
might indeed be anticipated, that elements so closely related 
as these are almost invariably found associated in nature. 

119. Characteristic Reactions. — The soluble chlorides, bro- 
mides, and iodides all give, with a solution of argentic nitrate, 
precipitates insoluble in water and acids. The iodide of silver 
may be distinguished from both the chloride and the bromide 
of the same metal by its yellow color and insolubility in aqua 
ammonia, in which the last two readily dissolve. Bromine and 
iodine may both be expelled from their salts by chlorine gas, 
when the first may be recognized by the red color which it im- 



§119.] QUESTIONS AND PROBLEMS. 211 

parts to ether or chloroform, and the last by the exceedingly 
characteristic blue color which it gives to starch paste. Flu- 
orine is easily discovered because its compounds, when heated 
in a glass tube with potassic bisulphate, yield hydrofluoric acid 
which etches the gla-s. This element, although closely allied 
to the other three, d.ffers so greatly in some of its chemical re- 
lations that it is doubtful whether it belongs to the same chem- 
ical series. 



Questions and Problems, 

1. It appears that 10 grammes of pure fluor-spar yields 17.436 
grammes of calcic sulphate [70]. Assuming that the atomic weight 
of calcium is 40, that of SO t 96, and also that the symbol of fluor- 
spar is CaF 2 , what is the atomic weight of fluorine? Ans. 19. 

2. How much fluor-spar and how much sulphuric acid must be 
used to generate sufficient hydrofluoric acid to neutralize 53 grammes 
of sodiC carbonate ? 

Ans. 39 grammes of fluor-spar and 49 of sulphuric acid. 

3. How much liquid hydrochloric acid, Sp. Gr. 1.1893, and how 
much MnOp will yield one litre of chlorine gas? 

Ans. 3.897 grammes of MnO„ and 17.06 grammes of hydrochloric 
acid. 

4. Fifty-nine grammes of metallic tin were dissolved in hydro- 
chloric acid 1 84], and into this solution chlorine gas was passed until 
all the tin was converted into perchloride. How many litres of hy- 
drogen gas were evolved in the first process, and how many of chlo- 
rine gas absorbed in the second ? Ans. 11.16 litres of each. 

5. Analyze reactions [66 and 79], and show in what way the 
chlorine gas acts as an oxidizing agent. 

6. Five grammes of liquid hydrochloric acid are mixed with a 
solution of argentic nitrate, the last being in excess. The precipi- 
tated argentic chloride was collected, washed, dried, and weighed. 
The weight was 3.206 grammes. Required the per cent of HCl in 
the solution. Ans. 16.31. 

7. One volume of rommon muriatic acid, Sp. Gr. 1.2, contains 
how many volumes of HCl gas ? 

Ans. 1 c. m. 3 , or 1 200 grammes, contains 0.489 grammes of HCl, 
or 315.8 c. in. 3 measured at 15° [9]. 

8. In order to make one litre of common muriatic acid of Sp. Gr. 



212 QUESTIONS AND PEOBLEMS. 

1.16, how much salt and how much sulphuric acid must be used, and 
how much water must be placed in the condenser? [81] 

Ans. 598.9 grammes of salt, 1003. grammes of sulphuric acid, and 
786.3 grammes of water. 

9. On what does the economy of the process [80] over [81] de- 
pend ? 

10. The reaction [82] is said to prove that both hydrogen and 
chlorine gas have molecules consisting of two atoms. On what pos- 
tulates does the proof rest? (17) (19.) 

11. One litre of hydrochloric acid gas will yield by [83] how 
many litres of hydrogen gas ? Ans. | of a litre. 

12. Point out the differences between the reactions [84, 85, 86, 
and 87], and the relations on which the differences depend. 

13. Show that the compounds of chlorine and oxygen may be re- 
garded as compounds of chlorine and hydroxyl, less a certain number 
of molecules of water. What atomicity would it then be necessary 
to assign to chlorine ? 

vii vn 

Ans. For one case, (#0) 7 vn CI — 3i7 2 = (HO) -010,0,0. 

14. It has been found by very careful experiments that 100 parts 
of potassic chlorate yield by [88] 60.85 parts of potassic chloride; 
and further, that 100 parts of potassic chloride give by precipitation 
192.4 parts of argentic chloride. Assuming that the symbols of 
these compounds are those given above, what must be the atomic 
weights of chlorine, potassium, and silver? It is also assumed, as 
found by previous experiments, that the atomic weight of oxygen is 
16, and that 100 parts of silver combine with 32.87 of chlorine. 

Ans. CI = 35.5, K = 39.1, Ag = 108. 

15. The chlorine gas evolved from 1.740 grammes of Mn0 2 is 
passed into a solution of potassic iodide. How much iodine will be 
thus set free? Ans. 5.081 grammts. 

16. Bromine and iodine form both with hydrogen and oxygen 
compounds similar to those of chlorine. Compare together the sev- 
eral compounds and point out the resemblances and differences in 
their properties. (See Miller's Chemistry.) 



§ 123.] SODIUM. 213 



Division IIL 

120. SODIUM. Na = 23. — Monad. Combined with 
chlorine it forms common salt, a substance which is very 
widely distributed throughout nature. It aLo enters into the 
composition of a few other minerals as an essential constituent, 
and several of its salts find important applications both in the 
arts and in common life. 

121. Metallic Sodium. Na~Na. — Soft, white metal with 
brilliant lustre, but rapidly tarnishing in the air. Sp. Gr. = 
0.97. Fuses at 90°, and boils at a red heat. When heated 
in the air, it burns with intensely yellow flame. Decomposes 
water at the lowest temperatures. Prepared by distilling in an 
iron retort a mixture of sodic carbonate and charcoal. 

TVaX© 3 + 2 C = ESa-Sffa + 3 ®®. [89] 

Used in the extraction of aluminum, and in the chemist's labora- 
tory as a powerful reducing agent. 

122. Sodic Chloride (Common Salt). NaCl. — White crys- 
talline salt (Isometric, Fig. 7). Sp. Gr. = 2.078. Melts at 
red heat. Volatilizes at white heat. Soluble in about three 
times its weight of water. Obtained from salt-beds and by the 
evaporation of saline waters. An essential article of food. The 
source of almost all the sodium salts. Used for preserving meat. 

123. Sodic Carbonate (Sal Soda). Na 2 C0 3 . — The crystal- 
lized salt contains in addition 10 // 2 O, but effloresces in dry air. 
White soluble salt, having an alkaline reaction. Formerly pre- 
pared by the lixiviation of the ashes of certain 'marine plants 
called barilla. Now almost universally made from common 
salt by Leblanc's process. This consists, — First, in treating 
common salt with sulphuric acid, which converts sodic chloride 
into sodic sulphate. 

2N a CI + H 2 SO, = Na 2 SO, + 2 SSOl. [90] 

Secondly, in melting on the hearth of a reverberatory furnace 
the sodic sulphate with chalk and fine coal. 

bNa 2 SO± -f 20(7= 5Na 2 S + 20@®. [91] 

5Xa 2 S+7CaC0 3 = 

bNa 2 C0 3 + 5CaS, 2CaO + 2@® 2 . [92] 



214 sodium. [§ 124. 

Thirdly, by lixiviating the non-volatile product of the last re- 
action (called black-ball) with water, which dissolves only the 
sodic carbonate. Used in washing, in the manufacture of glass 
and soap, and in the preparation of other sodium salts. Also 
an important reagent in the laboratory. Precipitates from so- 
lution of their salts most of the metals, generally as carbonates. 

(CaCl. 2 + Na 2 C0 3 + Aq) =CaC0 8 + (2NdCl + Aq). [93] 

When fused in large excess with insoluble silicates or sulphates, 
it decomposes them. Sodic silicate or sulphate is formed, which 
is soluble in water, and metallic carbonates, soluble in acids. 

BaSO i + xNa 2 C0 3 = 

BaC0 3 + JVa 2 S0 4 + (x — 1) Na 2 CO & . [94] 

124. Acid Sodic Carbonate (Bicarbonate of Soda). B,Na=C0 3 . 
— The crystallized neutral carbonate, when exposed to an at- 
mosphere of carbonic anhydride, absorbs the gas and is converted 
into this product (a white powder). 

Na 2 C0 3 . \0H 2 O -f (S@ 2 = 2H,Na=C0 3 + dll 2 0. [95] 

Used, under the name of saleratus, for raising bread, and in the 
preparation of various effervescing powders. 

(B,Na-C0 3 + B.K=rjT 4 6 + Aq) = 

Cream of Tartar. 

(Na.K-C A H,0 Q -f H 2 + Aq) + @® 2 . [96] 

Rochelle Salts. 

125. Sodic Hydrate (Caustic Soda). Nn-O-H. — Amor- 
phous white solid, having very strong attraction for water, in 
which it dissolves in all proportions, evolving considerable heat. 
Solution powerfully alkaline and strongly caustic. Prepared 
by adding milk of lime to a solution of sodic carbonate. 

(Na 2 =C0 3 + Ca-(HO) 2 -f Aq) = 

Ca=€© 3 + (2Na-H0 + Aq). [97] 

To obtain the solid, the solution must be decanted from the in- 
soluble chalk ( CaCO s ) and evaporated to dryness. The solu- 
tion itself is a very valuable reagent in the laboratory, and a 
crude solution (lye) is used in the arts for making soap. 



§ ISO ] POTASSIUM. 215 

Caustic soda will completely neutralize the strongest acids. On 
evaporating the neutral solution, we obtain the sodic salt of the 
acid used. 

(NaO-H + HO-N0 2 + Aq) = 

NaO-N0 2 + H 2 + Aq). [98] 

(2NaO-II-\- (HO)f 0,0 2 + M) = 

Oxalic Acid. 

{{NaO)fC 2 2 + 2R 2 + Aq). [99] 

Sodic salts of weak acids have an alkaline reaction. 

12G. Oxides of Sodium. — Sodic Oxide, Na 2 =0. Sodic Per- 
oxide, Na.f{0~0). 

127. Sodic Nitrate ( Ch Hi Saltpetre or Cubic Nitre) . Na -N 3 . 
— A natural product found incrusting the soil in the desert of 
Atacama. Crystallizes in rhombohedrons resembling cubes. 
Much u-»ed for making nitric acid. 

128. POTASSIUM. ^=39.1. — Monad. An impor- 
tant constituent of felspar and mica, two very widely distrib- 
uted siliceous minerals. A constituent also of all fertile soils 
which are formed in part by the disintegration of rocks con- 
taining these minerals. By the action of atmospheric agents 
on the soil, soluble potassium salts are formed which, are ab- 
sorbed by the growing plants, whose allies are the chief source 
of the potassium salts of commerce. But these salts are now 
also obtained from the salt-beds of Stassfurtin Germany. 

129. Metallic Potassium. K~K. — Resembles sodium, but 
has a bluish tinge of color; Sp. Gr. = 0.865. Brittle at 0°. 
Soft at 15°. Melts at 55°. Sublimes in green vapors at a low 
red heat. Burns when heated in the air, and takes fire spon- 
taneously on water. Prepared by distilling in an iron retort 
the intimate mixture of potassic carbonate and charcoal obtained 
by charring crude tartar. Reaction same as [89], substituting 
A" for Na. More powerful reducing agent than sodium ; hence 
obtained with greater difficulty. More expensive, and less used 
on that account. 

130. Potassic Carbonate. K 2 CO % . — White deliquescent 
salt, with strong alkaline reaction. The crude salt {Pot-ashes 
of commerce) is obtained by lixiviating wood-ashes and evap- 
orating the lixivium. Purified by dissolving in a small quantity 
of boiling water, and crystallizing out the impurities. Largely 



216 POTASSIUM. [§ 131. 

consumed in the arts for manufacturing glass and soap, and for 
preparing other compounds of potassium. 

131. Acid Potassic Carbonate (Bicarbonate of Potash). 
JI,K=C0 3 . — White crystalline salt, prepared by passing C0 2 
through a strong solution of the neutral carbonate. Reaction 
like [95], substituting iTfor Na. 

132. Potassic Hydrate {Caustic Potash). P,K=0. — White 
amorphous solid, prepared like caustic soda [97], which it 
closely resembles, but is more deliquescent and more strongly 
alkaline. Forms with fats " soft soaps," while soda forms " hard 
soaps." Like caustic soda, an important reagent in the labor- 
atory. Precipitates from solutions of their salts most of the 
metals, generally as hydrates, but sometimes as oxides. In 
some cases the precipitate is soluble in an excess of the 
reagent. 

( Ca-S0 4 + 2K-(HO) + Aq) ■= 

Ca=(HO) a + (K 2 =S0 4 + Aq). [100] 

(2Ag-N0 3 + 2K-(RO) + Aq) = 

Ag& + (H 2 + 2K-N0 3 + Aq). [101] 

([A! J CI, + 6K-(RO) + Aq) = 

[ AlJ!(HO)« + (GKCl + Aq). [102] 

[AIJI(HO) 6 + (6K-HO + Aq) = 

(K^O^AQ + QILO + Aq). [103] 

',•■" Potassic Aluminate. 

133. Oxides of Potassium. — Potassic Oxide, KfO. Po- 
tassic Dioxide, Kf(O-O). Potassic Tetroxide, 10(0-0- O-O). 

134. Potassic Chloride (Sylvine). KCL — Isomorphous with 
Na CI. Found associated with Carnallite (K CI . M<jCL 2 . GJI^ O) 
in the mines of Stassfurt. 

135. Potassic Nitrate (Nitre). KN0 3 . — White crystalline 
salt. Dimorphous. Usual form of crystals orthorhombic pri;ms, 
but under certain conditions crystallizes in rhombohedra like 
NaN0 3 (Hexagonal). Melts at 339° without decomposition. 
Is decomposed at a red heat, giving off a mixture of oxygen and 
nitrogen gas. Deflagrates on glowing coals. Nitre is a natural 
product, and is chiefly used in the manufacture of gunpowder. 
It is also employed in curing meat, and the fu^ed salt (sal pru- 
nelle) is a useful medicine 



§ 138.] QUESTIONS AND PROBLEMS. 217 

136. Characteristic Reactions. — Salts of potassium are dis- 
tinguished from those of sodium by giving a precipitate with an 
excess of tartaric acid and with acid platinic chloride. 

{KCl + H, H- CJh 0, + Aq) = 



Tartaric Acid. 



H,K=C 4 H 4 6 + (HCl + Aq). [104] 

Acid eutassic Tartrate. 



(2 KCl + Pta ff 2 + Aq) = 

Pt£I K 2 + (2ffCl+Aq). [105] 

137. Lithium, Rubidium, and Ccesium are found in very 
minute quantities in certain mineral waters, in lepidolite mica, 
and in a few other rare minerals. Tiiey are always associated 
with potassium and sodium, to which they are closely allied in 
all their chemical relations. They form with sodium and po- 
tassium a series of electro-positive elements qtiite as well marked 
as the series of electro-negative elements of the previous group; 
and, following the same law, the most electro-positive elements 
are the lowest in the series and have the highest atomic weights. 
Hence, therefore, the chemical energy of the elements of this 
group, as manifested by the strength of their affinities for ele- 
ments of the opposite class, like those of the chlorine group, 
increases as we de-cend in the series. 

13<S. Characteristic Reactions. — The compounds of each of 
the five "alkaline metals" impart a peculiar color to the flame 
of the Bunsen lamp. These colored flames, when examined 
with the spectroscope, exhibit characteristic bands, by which 
the elements may be distinguished, and both rubidium and cae- 
sium were discovered by this means. (Chapter XVI.) 



I Questions and Problems. 

1. What is the Sp. Gr. of sodium vapor? Ans. 23. 

2. What is the weight of one litre of sodium vapor at 1,093°, but 
under the normal pressure? [9] and (1). 

Ans. Weight of hydrogen gis under the conditions nfrmed is \ of 
a crith. Hence, weight of sodium vapor is 4.6 criths or 
0.4121 of a gramme. 

3. In fie preparation of sodium [89] what weight of metal ought 
to be obtained from 20 kilos, of sodic carbonate, and how many litres 

10 



218 QUESTIONS AND PROBLEMS. 

of carbonic oxide gas should be formed for every gramme of sodium 
obtained ? 

Ans. 8.680 kilos, of sodium and 1.456 litres of carbonic oxide. 

4. One cubic decimetre of rock-salt contains how many cubic 
decimetres of metallic sodium, and how many litres of chlorine gas? 

Ans. 0.8422 d.~m? of sodium and 396.5 litres of chlorine. 

5. To what extent is the solubility of common salt influenced by 
the temperature? (Fig. 2, page 108.) 

6. Given the specific heat of common salt (0 214), and the atomic 
•weights of its elements (sodium and chlorine), to find its symbol. 

7. How much carbonate of soda can be made from 500 kilo- 
grammes of common salt ? How much sulphuric acid ? How much 
coal and how much chalk are required in the process, according to 
the theory ? 

Ans. 453 kilo*, of NaC0 3 , 418.8 kilos, of H 2 SO v 205 kilos, of C, 
and 598.2 of CaCO z . 

8. What relation ought the price of crystallized carbonate of soda 
to bear to that of the dry salt, if the intrinsic value is alone consid- 
ered? Ans. Price of dry salt 2.7 of crystallized. 

9. In order to convert ten kilogrammes of crystallized sodic car- 
bonate into acid carbonate, what volume of C0 2 will be absorbed ? 

Ans. 780.3 litres. 

10. Whit is the difference between the two sodic carbonates, and 
what is the reason for the name acid carbonate ? (36). 

11. What volume of C0 2 can be obtained from 3.72 grammes of 
acid solic carbonate? [96]. Ans. 1 litre. 

12. The symbol of sodic hydrate maybe written Na-O-H, or 
Ka-Ho, or (XaO)-II, and to what three possible views of its consti- 
tution do these symbols correspond ? [70] (235). Why should the 
radicals 110 or NaO be monads, and what advantage would be 
gained by writing the symbol in one way or the other? (22) and 
(28). 

13. Why does calcic hydrate, a comparatively weak base, decom- 
pose sodic carbonate? (21) (o2). 

14. A solution of caustic soda was exactly neutralized by 0.630 
of a gramme of crystallized oxalic acid (Ho.fC 2 2 . 2fl 2 0). ^Yhat 
■weight of sodium does it contain ? Ans. 0.230 of a gramme. 

15. In what different ways may you write the symbol of potassic 
nitrate? Illustrate by digrams like those of (34). State what 
rules must be followed in grouping the atoms. (22, 28, 34 and 69.) 

Ans. K-NO v KO-N0 2 , or K-0-N0 2 . 



QUESTIONS AND PROBLEMS. 219 

16. What conclusions may be drawn in regard to the distribution 
of the soluble salts of sodium and potassium based on the nature of 
the plants from which they are obtained ? 

1 7. On what relations of solubility does the process of purifying 
potassic carbonate depend ? 

18. If in a chemical process potassic or sodic carbonates may be 
used indifferently, what relation ought thtir prices to bear to each 
other in order that they may be used with equal profit? 

Ans. 138 : 106. 

19. Analyze equations [100, 101, 102, 103], and show that the 
various symbols are written in conformity to the rules referred to 
above, No. 15. 

20. If a saturated solution of nitre is made at 38°, and subse- 
quently cooled to 10°, what proportion of the salt will crystallize 
out ? (Fig. 2.) Ans. Two thirds. 

21. The difference between the two kinds of soap corresponds to 
what difference of properties between sodic and potassic carbonate ? 

Ans. The one effloresces and the other deliquesces in the air. 

22. Draw diagrams illustrating the constitution of the different 
potassic oxides. (34.) 

23. Why would not the salts of sodium be precipitated by the 
same reagents used in [104 and 105] ? Apply the same principle to 
the interpretation of the other reactions of this section. 



220 SILVER. [§ 139. 



Division IV. 

139. SILVER. Ag = 108. — Monad. Found in small 
quantities in nature, chiefly in the metallic state, or in com- 
bination wiih chlorine, sulphur, arsenic, or antimony. 

140. Metallic Silver. Ag-Ag? — Sp. Gr. 10.474. Fuses 
at about 1,000°. The principal ores are 

Native Silver Ag-Ag, 

Horn Silver -Agd, 

Silver Glance Ag 2 S, 

Light-red Silver Ore (Proustite) (AgS) ; ^As, 

Dark-red Silver Ore (Pyrargyrite) (AgS) s -Sb. 

These ores are found chiefly in mineral veins either by them- 
selves or associated with ores of lead and copper, with which 
they are frequently smelted, and the silver subsequently sepa- 
rated from the regulus thus obtained. Silver does not oxidize 
when heated in contact with the air, and for this reason is 
readily separated from lead in the process of cupellation. 

xAg 2 . yPb -f- lyO~-0 = xAg-Ag -f yPbO. [10G] 

The cupel furnace is so arranged that the melted litharge (PhO) 
runs off as fast as formed, and leaves the silver pure. Melted 
silver can dissolve about twenty-two times its volume of oxy- 
gen gas ; but the gas is given off, in great measure, when the 
metal solidifies. 

141. Argentic Nitrate. AgN0 3 . — The most important sol- 
uble salt of silver. Obtained by dissolving silver in dilute ni- 
tric acid. 

3 Ag-Ag + (SHN0 3 + Aq) = 

(QAgN0 3 + 4ff 2 + Aq) + 2E!FS). [107] 

White crystalline solid which melts at 219°. Fused salt is 
called lunar caustic, and is much used in surgery as a cautery. 
Argentic nitrate, although not changed by the light when pure, 
is readily decompo-ed when in contact with organic matter, and 
the black stain of metallic silver thus formed cannot be removed 
by washing. Hence its application for making hair dyes and 



§ 143.^ SILVEE. 221 

indelible ink. It is also used in large quantities in the art of 
photography. 

142. Argentic Chloride. AgCl. — White crystalline solid 
(Fig. 7). Melts at about 260°, and on cooling forms a horny 
sectile mass, whence the mineralogical name, horn silver. Pre- 
pared by adding to a solution of argentic nitrate any soluble 
chloride. 

(AgNO s + JVa a + Aq) = AgCl + {NaNO, + Aq). [1 08] 

We thus obtain a white curdy precipitate, which is insoluble in 
water and acids, but soluble in ammonia, in potassic cyanide, 
and in sodic hyposulphite. Owing to a partial reduction, the 
white powder blackens in the light, especially in the presence 
of organic matter and an excess of argentic nitrate. On this 
property is based the ordinary process of photographic printing. 
In contact with dilute acids, argentic chloride is very readily 
reduced by metallic zinc. 

2Ag Cl-\- Zn = ZnCl 2 + Ag 2 . [109] 

It may also be reduced by hydrogen or hydrocarbon gas passed 
over the chloride in a heated tube. 

2Ag€l + EHS = Ag-Ag + 2511(31. [110] 

In the process of electro-plating, argentic chloride, dissolved in 
an aqueous solution of potassic cyanide, is decomposed by the 
electric current. (91). 

143. Argentic Bromide, AgBr, and Argentic Iodide, Agl, 
resemble argentic chloride, and are formed in a similar way. 
The last, however, has a yellow color, and is insoluble in am- 
monia. In presence of an excess of argentic nitrate, and after 
exposure to light, they are at once reduced to the metallic state 
by solution of ferrous sulphate. Before exposure the reduction 
takes place very slowly, and on this reaction is based the art 
of photography. The steps of the process are: 1. Spreading 
over a glass plate a film of collodion, holding in solution a mix- 
ture of metallic bromides and iodides ; 2. Immersing the coated 
plate in a solution of argentic nitrate until a mixture of argen- 
tic bromide and iodide is formed in the film ; 3. Exposing the 
plate to light in the camera, where the image formed by a lens 
falls upon it ; 4. Developing the latent image by a solution of 



222 THALLIUM. — GOLD. [§ 144 

ferrous sulphate ; 5. Dissolving out the undecoraposed silver 
salt by a solution of sodie hyposulphite. 

144. Argentic Oxide. Ag 2 0. Argentic Peroxide. Ag t O v 
— The first is very slightly soluble in water, and the solution 
has an alkaline reaction. 

145. Characteristic Tests. — Most silver compounds may be 
reduced to pure silver before the blow-pipe ; and whenever 
they are brought into solution the silver cau be recognized and 
the amount very accurately determined by the reaction just 
given. [108]. Silver is remarkable for forming anhydrous 
salts ; and whenever we wish to determine the molecular weight 
of an acid, it is generally best to analyze its silver salt. (G8). 



Division V. 

146. TFIALLIUM. Tl = 204. — Usual quantivalence 
one, but atomicity probably three. A very rare element, found 
in some varieties of pyrites. Its oxide, Tl 2 0, is soluble in 
water, and absorbs carbonic anhydride from the air. Its vapor 
imparts a green color to the flame of a Bunsen lamp, and shows 
a single green band in the spectroscope. 



Division VI. 

147. GOLD. Au == 197. — Triad. Probable molecular 
symbol of metal, Au=Au. Almost always found in the native 
state, or only slightly alloyed with other metals. The only 
well-defined native compounds are those with Tellurium. 
Very sparingly but very widely disseminated through many of 
the crystalline rocks and in the alluvium resulting from their 
disintegration. In the gold-bearing rocks the metal is frequently 
found accumulated to a greater or less extent in veins of quartz 
(auriferous quartz). It is also constantly associated in minute 
quantities with other metallic ores, especially with those of sil- 
ver, and in some localities the veins of iron and copper pyrites 
yield large amounts of the precious metal. It is extracted 
either by simple washing or by bringing the finely pulverized 
ore in contact with metallic mercury, which has a great affinity 
for gold and picks out the minute particles from the mass of 



§ 147.] GOLD. 223 

refuse. The process is very simple, and the cost of the product 
depends, to a great extent, on the very large amount of material 
which must be handled; for gold ores do not on the average 
contain but a few ounces of metal to the ton. From the re- 
sulting amalgam the mercury is recovered by distillation, and 
the residual metal may then be melted and cast into bars. The 
gold thus obtained, however, is more or less alloyed, chiefly 
with silver, and is refined before being used for coinage. This 
is best accomplished by dissolving the metal in aqua-regia, 
evaporating to dryness to remove the excess of nitric acid, dis- 
solving in a large volume of water, and precipitating the gold 
with ferrous sulphate. Lastly, the precipitate is collected and 
melted under borax. If the proportion of alloy is very large, 
it is best removed by boiling the metal with nitric or sulphuric 
acid. When nitric acid is used for parting gold from silver, 
the separation is not complete when the amount of gold is 
more than one fourth of the weight of the alloy ; and since in 
most cases the alloy must be first reduced to this proportion, 
the process is called quartation. When sulphuric acid is used, 
the amount of gold must not exceed one fifth. 

Gold has been called the king of metals ; for it not only pos- 
sesses the qualities distinguishing a metal in their highest per- 
fection, but also, under all ordinary conditions, preserves its 
brilliant lustre unimpaired. With the exception of platinum, 
iridium, and osmium, gold is the densest solid known ; Sp. Gr. 
19.34. It may be drawn into wire of such fineness that three 
kilometres only weigh a single gramme, and may he beaten 
into leaves not more than one ten-thousandth of a millimetre 
thick. Gold has a familiar yellow color, but thin leaves trans- 
mit a green light. It has been found that an exceedingly thin 
film of gold attached to the surface of a glass plate, and heated 
to a temperature not exceeding 315°, loses its metallic lustre 
and appears ruby-red by transmitted light ; and finely divided 
gold, when suspended in water or melted into glass, imparts to 
the medium the same beautiful color. Gold is nearly as soft as 
lead, and pieces of pure gold may be welded together without 
heat by pressure or concussion, as in dentistry. In order to 
increase its hardness it is alloyed with copper. The standard 
gold of both the United States and the French coinage contains 
one tenth copper, that of the English one twelfth of the same 



224 GOLD. 



[§ H7. 



alloy. Gold melts at about 1,100°. It is only slightly volatile 
at the highest furnace heat ; but before the compound blow-pipe 
it is dispersed in purple vapor. It is an excellent conductor of 
heat and electricity, but is inferior in this respect both to silver 
and copper. 

Gold is not dissolved by any of the common acids, and is not 
attacked by the fused caustic alkalies. It enters, however, into 
direct union both with chlorine and bromine, and is readily dis- 
solved by any liquid mixture which liberates chlorine. The usual 
solvent is a mixture of lour parts of hydrochloric acid with one 
of nitric acid, called, on account of its power of dissolving gold, 
aqua-regia. 

Au=-Au + (2HtfO s + QHCl + Aq) = 

(2AuCl 3 -\-AH 2 + Aq) + 2Sm [111] 

When gold is dissolved in aqua-regia, if hydrochloric acid is 
used in excess, the solution, evaporated at a gentle heat, yields 
yellow needle-shaped crystals, which appear to be a molecular 
compound of AuCl 3 with HCl. If, however, the evaporation 
is pushed still further, but at a temperature not exceeding 120°, 
a red crystalline mass is obtained, which is essentially Auric 
Chloride, AuCl 3 , although it is difficult to expel the last traces 
of HCl without still further decomposing the salt. If this pro- 
duct is heated above 160° it loses two atoms of chlorine, and 
there is left a pale-yellow, sparingly soluble powder, which is 
Aurous Chloride, Au CI, and at 200° this last is also decom- 
posed and reduced to metallic gold. Auric chloride is deli- 
quescent, and yields an orange-colored solution easily distin- 
guished from the solution of AuCl 3 . HCl, which is yellow. It 
also forms yellow crystalline salts with the alkaline chlorides, 
similar in constitution to the compounds with HCl. Their for- 
mulas are AuCl 3 . KCl . 5H 2 0, and AuCl 3 . NaCl.4H 2 0. In 
like manner it unites with ammonic chloride and with the chlo- 
rides of most of the organic bases, forming crystallizable salts, 
which are often employed to determine the molecular weight of 
these alkaloids. Auric chloride is a very unstable compound, 
and is readily reduced to the metallic state. Solutions of fer- 
rous sulphate, of antimonious chloride, of oxalic acid, and of 
sulphurous acid, all precipitate the gold in a finely-div'ded 
state. Phosphorous and hypophosphorous acid and solutions 



§ 147.] GOLD. 225 

of their salts produce the same effect, as do also phosphorus it- 
self and many of the metals. The brown gold powder thus ob- 
tained is much used for gilding porcelain. A solution of stan- 
nous chloride mixed with stannic chloride produces in neutral 
solution of auric chloride a beautiful purple precipitate called 
Purple of Cassius, which is much used for coloring glass and 
porcelain. The compound contains both gold and tin combined 
with oxygen, but its chemical constitution is still in question. 
Metallic tin gives a similar precipitate. There appear to be 
two iodides of gold, Aul and Aul 3 , but only one bromide, AuBr 3y 
has been described. There are also two oxides, Au 2 3 and 
Au 2 0. The first acts as an acid, the second as a very feeble 
basic anhydride. The following reactions illustrate the forma- 
tion and relations of these compounds. 

(AuCl 3 + 6K-0-H4- Aq) = 

{KfOfAu + 3KCI + 3R 2 + Aq). [112] 

KiOfAu + 3H-OC,H 3 + Aq) = 

JBfOfAu-j- (3K- 0-C 2 H 3 + Aq). [113] 

ZHiOiAu = Au 2 3 + 3H 2 0. [114] 

To obtain the=e reactions the solution of AuCl 3 should be boiled 
after the addition of KO-H and then acidified with acetic acid. 
The precipitate thus obtained has, when dried, the composition 
of Au 2 3 . The compound Au 2 is obtained as an insoluble vi- 
olet powder by digesting Au CI with a solution of caustic alkali. 

(2 Au CI + 2JVa-0-H+ Aq) = 

Au 2 + {2NaCl + H,0 + Aq). [115] 

It does not enter into direct combination with acids, but there 
is an hyposulphite of gold and sodium which plays an impor- 
tant part in photography, and appears to have the formula 
Au,Na = 2 =(S-0-S). Singularly, however, gold is not precipi- 
tated from the solution of this salt by the ordinary reagents. 
There are two sulphides of gold, Au 2 S 3 and Au 2 S. The first 
is precipitated by II 2 S from a cold solution and the last from a 
boiling solution of AuCl 3 by the same reagent. They both 
dissolve in alkaline sulphides and form sulphur salts. Thus 

Au 2 S 3 + (QK-S-II+ Aq) = 

{2KfSfAu + Aq) -f 3J7 2 & [116] 
10* o 



226 QUESTIONS AND PROBLEMS. [§148. 

148. Characteristic Reactions. — With the exception just 
noticed, gold, when in solution, can be distinguished by the fact 
that it is precipitated by ferrous sulphate, provided the solution, 
though acid, does not contain an excess of nitric acid. 

(2AuCl 3 + 6Fe--0.,=SO, + Aq) = 
An=-An + (lFe 2 ybl 6 + 2lFe 2 yO^S0 2 ) 3 + Aq). [117] 

The formation of purple of Cassius, and the easy reduction of 
all the compounds to the metallic state by simple ignition, are 
other indications by which the presence of gold may be readily 
recognized. The reduced gold, even when in fine powder, ac- 
quires its peculiar lustre if rubbed against a hard surface, as in 
the process of burnishing. Besides the important uses of gold 
for coinage and for articles of ornament or luxury, the metal is 
peculiarly well adapted, both by its softness and its power of 
resisting corrosive agents, for its applications in dentistry. It 
is also largely employed in the various methods of gilding, 
which consists either in directly applying thin gold-leaf to the 
surface to be covered, or, when the surface is metallic, by de- 
positing upon it a thin film of gold with the aid of galvanism 
or by the simple action of chemical affinity. 



Questions and Problems. 

1. Given the percentage composition of Proustite. Silver, 65.45; 
Sulphur, 19.39; Arsenic, 15.16. Required the symbol. 

Ans. Ag 3 S 3 As. 

2 How much greater is the per cent of silver in Proustite than 
in Pyrargyrite ? Ans. 5.68 per cent. 

3. Draw diagrams illustrating the molecular constitution of the 
different silver ores. 

4. Analyze reaction [107], and point out the difference between 
it and the class of reactions of which [64 J is the type. 

5. If a given mass of argentiferous lead contains three fourths of 
one per cent of silver, how many kilogrammes of litharge will be 
made in the process of cupellation to each kilogramme of silver ex- 
tracted, and how many cubic metres of oxygen gas will be absorbed 
by the process ? 

Ans. 142.5 kilos, of litharge, and 7.134 ml 3 of oxygen. 



QUESTIONS AND PROBLEMS. 227 

6. One gramme of silver treated as indicated by [107] and [108] 
yielded 1.328 grammes of argentic chloride. What is the atomic 
weight of silver ? The atomic weight of chlorine is assumed to be 
known, 35.5, and also the specific heat of argentic chloride, 0.091. 

Ans. 108. 

7. One gramme of argentic chloride reduced by hydrogen [110] 
yielded 0.7526 of a gramme of silver. What is the atomic weight 
of silver ? The same values are assumed as in the last problem. 

Ans. 108. 

8. One gramme of argentic oxalate yields when heated 0.7105 of 
a gramme of silver. We have reason to believe that oxalic acid is 
bibasic. W r hat is its molecular weight ? (68). Ans. 90. 

9. W T rite the reactions of sulphurous acid and of oxalic acid on 
solution of auric chloride, assuming that sulphuric acid in one case, 
and C0 2 in the other, are a part of the products. 

10. What evidence do you find of the quantivalence of gold in the 
above sections ? 

11. Does gold act as an acid or a basic radical? 

12. What is the chief chemical characteristic of gold ? 

13. There has been a question about the cause of the color which 
purple of Cassius imparts to glass and porcelain glaze. Do the facts 
stated above explain this phenomenon ? 



228 BOKON, [§ 149. 



Division VII. 

149. BORON. ^=11. — Triad. Very sparingly distrib- 
uted. Always found in combination with oxygen. In boric acid 
and in various borates, including the minerals Datholite and 
Danburite, boron is the electro-negative element, while in Axi- 
nite and Tourmaline, and in many artificial salts, it acts the part 
of a basic radical. The elementary substance (B=B?) may be 
obtained both in an amorphous and a crystalline form. The 
first is obtained by decomposing boric anhydride with sodium. 

B. 2 3 -f SNd-Na — 3Na 2 + B=-B. [118] 

It is an infusible dark-brown powder, which soils the fingers 
and dissolves slightly in water. At about 300° it takes fire in 
the air and burns into B 2 3 , and it is also oxidized when heated 
with sulphuric acid or with the alkaline nitrates, sulphates, car- 
bonates, or hydrates. It decomposes nitric acid even when 
slightly concentrated and cold. 

B--B + 3R 2 = Of SO, = B 2 3 + 3R 2 + 3S0 2 . [1 1 9] 

B=-B + 0>KNO 3 — 2Kf OiB -f <oN0 2 . [120] 

Boron is one of the very few elements which unite directly with 
nitrogen. 

B*B + N*N= 2B=K [121] 

If amorphous boron is heated intensely in a closed crucible, it 
becomes much denser, and is then less easily oxidized. It dis- 
solves in melted aluminum, and when the molten metal sets, the 
boron crystallizes in quadratic octohedrons (75) more or less 
highly modified. These crystals are nearly as hard as the dia- 
mond, have an adamantine lustre, and Sp. Gr. == 2.68. They 
may also be obtained directly from boric anhydride, which is 
decomposed by aluminum. 

[i? 2 ] + B 2 3 = [44] 3 + B=B. [1 22] 

The crystals thus prepared are sometimes nearly colorless, 
but more frequently they have a yellow or red color, and some- 
times the color is so deep that they appear black. They are 



§ 150.] BORON. 229 

probably never wholly pure, and it is worthy of remark that 
they sometimes, if not always, contain a considerable quantity 
of carbon. They resist the action of all acids, and even of fused 
nitre, but are oxidized when fused with acid potassic sulphate. 
It appears, from recent investigations, that the so-called graphi- 
toidal boron, which is formed with the crystals just mentioned, 
is a compound of aluminum and boron. 

150. Boric Acid. H^O^B. — A product of volcanic action. 
Found in some natural waters, and has been detected in the 
waters of the ocean. It is collected in large quantities, but in 
an impure condition, from the hot vapors of the "fumerolles" 
in the Maremma of Tuscany. The pure acid is best prepared 
from borax by the reaction 

(m.fOrB,0 5 + 2HCI +5ff :i O + Aq) = 

4EfOfB+(2NiiCl+Aq). [123] 

The hydrochloric acid should be mixed with a hot saturated so- 
lution of borax, which as it cools deposits boric acid in white 
nacreous crystalline scales. Boric acid is sparingly soluble 
in cold water, but dissolves in three times its weight of boiling 
water. It is also soluble in alcohol, and imparts to the flame 
of burning alcohol a peculiar green tint, which exhibits in the 
spectroscope five well-marked green bands. The solution both 
in water and in alcohol cannot be evaporated without loss, as 
the vapor always takes with it an appreciable amount of the 
acid. The solution evaporated on turmeric paper changes the 
color to brown, like an alkali, but it affects litmus paper like 
other weak acids. At the temperature of 100° it loses one 
atom of water. 

Hf OfB = H-O-BO + H 2 0. [1 24] 

The compound HfOfB is called orthoboric acid. The pro- 
duct H-O-BO is frequently described as the first anhydride of 
this acid, and is called metaboric acid. If this is heated to a 
still higher temperature two molecules unite, while at the same 
time they lose another atom of water, forming the second and 
last anhydride, boric anhydride. 

2H- O-BO = B 2 O s + H 2 0. [1 25] 

At a red heat B 2 3 fuses to a viscid glass, which remains clear 



230 BOEON. [§ 151. 

as it cools, but soon becomes opaque and crumbles if exposed 
to the air. It also forms fusible compounds with the metallic 
oxides. Hence the use of boric acid and the borates as fluxes. 

151. Borates. — It is evident from the principles of (38) 
that, besides orthoboric acid, many others are theoretically pos- 
sible. Thus : — 

in 
Boric Acid B 3 =0 3 =B, 

Diboric Acid Hf A =(B- O-B), 

TriboricAcid B^0 5 =(B-0-B-0-B), 

Tetraboric Acid H 6 iO b i(B-0-B-0-B-0-B), 

Polyboric Acid H n ^ O n+2 (B n O n "$* 

These may be regarded as formed by the coalescing of sev- 
eral molecules of orthoboric acid, and the elimination from this 
condensed molecule of a sufficient number of molecules of water 
to set free the number of oxygen atoms required to cement to- 
gether the atoms of boron in the resulting radical. By elimi- 
nating additional molecules of water, we may obtain from either 
of the above acids a series of anhydrides (distinguished as the 
first, second, &c, anhydrides), and the number of pos.-ible an- 
hydrides in any case is equal to the number of pairs of hydro- 
gen atoms which the acid contains. It must be understood that 
all these possible forms are not real compounds. Indeed, only 
the three already mentioned have been actually prepared ; but 
there are several borates whose constitution is best explained 
when we regard them as salts of acids derived from orthoboric 
acid in the way just indicated. The most important of these 
is common borax, which may be regarded as the sodium salt of 
the second anhydride of tetraboric acid. 

152. Borax, Na.f 0./(B--0.fB-0-B=0.fB) .10 #,0, was orig- 
inally brought from a salt lake in Thibet, and was called Tincal. 
It al-o occurs in large crystals in the mud of Borax Lake, in 
California, and it has been found in solution in many mineral 
springs, and even in minute quantities in the ocean. Is man- 
ufactured in large quantities from the crude boric acid of the 
Tuscan lagoons. White crystalline salt, which when heated 
gives up its water of crystallization. At a red heat melts to a 
transparent glass, which has the property of dissolving almost 



§ 153.] BORON. 231 

all the metallic oxides. Many of them impart to the glass 
characteristic colors ; and these reactions, which are readily ob- 
tained with a small bead of borax supported by a loop of plat- 
inum wire, are useful blow-pipe tests. It is also used for solder- 
ing metals, for making enamels, for fixing colors on porcelain, 
and as a flux in various metallurgical processes. The ordinary 
crystals contain as above 10B 2 O, and belong to the monoclinic 
system ; but the salt can be crystallized with only hll 2 in oc- 
tahedrons belonging to the isometric system. 

153. Boric CMoride, BCI 3 , can be obtained by passing chlo- 
rine gas over an intimate mixture of B 2 3 and carbon, heated 
to a red heat in a porcelain retort. 

B 2 3 + 3 C + 3 Gl- CI = 3 CO + 2BCl 3 . [126] 

It is a very volatile liquid (Sp. Gr. 1.35 at 7°), boiling at 17°, 
and yielding a dense vapor whose Sp. Gr., as found by experi- 
ment, is 5G.85 ; chiefly interesting as establishing the quanti- 
valence of boron. It is at once decomposed by water. 

BCI 3 -\-3IT 2 — II 3 -=O s -=B+ ZHGl. [127] 

154. Boric Bromide, BBr 3 , prepared like the chloride, is a 
volatile liquid (Sp. Gr. 2.60), boiling at 90°, and giving a vapor 
whose Sp. Gr. has been found by experiment equal to 126.8. 
Decomposed by water like the chloride. 

155. Boric Fluoride, BF 3 , is best prepared by intensely 
heating a mixture of B 2 3 and fluor-spar. 

2B 2 3 + 3 CaF 2 = Ca 3 W 6 lB 2 + 2BF 3 . [128] 

A colorless gas, whose Sp. Gr. has been found by experiment 
equal to 31.2. This gas is eagerly absorbed by water, which 
dissolves seven hundred times its volume and forms a corrosive 
acid liquid called boroflaoric acid, whose constitution is not well 
understood. If its composition is that usually assigned to it, its 
formation will be expressed by the reaction 

2BF 3 + 3R 2 = B 2 3 . 6HF. [129] 

The same compound may be also prepared by dissolving B 2 3 
in HF -\- Aq, and then concentrating the solution. 

If borofluoric acid is largely diluted with water, one fourth 



232 QUESTIONS AND PROBLEMS. [§156. 

of the boron separates in the form of boric acid, and there is 
left in solution what has been called hydrofluoboric acid. 

(A(B 2 O s .eBF)+Ag) = 

2& s -OiB+ (Q{HF.BF 3 ) + 6# 2 + Aq). [130] 

Hydrofluoboric acid forms salts with basic radicals, and the 
compound with potassium may be formed by the action of boric 
acid on a dilute solution of potassic fluoride. 

(SKF + 2fffOfB+Aq) = 

2{KF.BF 3 ) + (QK-0-H+ Aq). [131] 

156. Characteristic Reactions. — The peculiar green color 
which boric acid imparts to an alcohol or blow-pipe flame is the 
best indication of its presence, and this test is made still more 
decisive by analyzing the colored light with the spectroscope. 
The acid, however, must first be set free before the reaction 
can be obtained. In many of its relations boron resembles 
carbon. 



Questions and Problems. 

1. Write the reaction of sulphuric acid on solution of borax. 

2. What test can be applied to determine when an excess of sul- 
phuric acid has been added ? 

3. Define an ortho acid, regarding orthoboric acid as a type of 
the class. 

4. Make a table showing the relations of the various possible de- 
rivatives of boric acid. 

5. The empirical symbol of boracite is Mg 3 Vj B s . What is its ra- 
tional symbol, and what is its relation to the ortho-borates ? 

6. Boric sulphide, B 2 S 3 , may be prepared by passing over a mix- 
ture of carbon and boric anhydride the vapor of carbonic sulphide, 
CS r The products are 2B 2 S 2 and GCO. Write the reaction. 

7. Boric sulphide is readily decomposed by water, giving boric 
acid and sulphuretted hydrogen. Write the reaction. 

8. In reaction [126] what double affinities are called into play? 

9. In what respect do you find reaction [131] remarkable? 

10. What evidence do you find of the prevailing quantivalence of 
boron ? Are there any facts which would indicate that boron is a 
pentad ? 



§ 158.] NITROGEN. 233 



Division VIII. 

157. NITROGEN. N= 14. — Pentad, but as frequently 
trivalent or univalent. Chief constituent of the atmosphere; 
but to this and the materials of organized beings it is almost 
exclusively confined. It is the characteristic ingredient of ani- 
mal tissues, which are composed mainly of the four elements 
carbon, hydrogen, oxygen, and nitrogen. Vegetable tissue*, on 
the other hand, consist chiefly of only the first three of these 
elements ; but nitrogen is never entirely absent from plants, and 
is an essential ingredient of many important vegetable products, 
as, for example, of the albuminoid compounds and of the vege- 
table alkaloids. Nitrogen is marked by weak affinities, and 
hence its compounds are usually unstable, as is illustrated by 
the well-known tendency of animal substance to decay. 

158. Nitrogen Gas, N=J¥, constitutes four fifths of the vol- 
ume of the atmosphere, and can be obtained in a pure condi- 
tion, — First, by slowly or rapidly burning phosphorus in a con- 
fined volume of air. Secondly, by passing air over ignited 
copper-turnings, which combine with the oxygen. Thirdly, by 
passing chlorine gas through a solution of ammonia, — 

(8ff 3 N+ Aq) + 3 CI- CI = (Gff.NCl + Aq) + MK [132] 

Fourthly, by heating ammonic nitrite or a mixture of potassic 
nitrite and ammonic chloride, — 

{H,N)-0-NO = 2ff 2 + NiN. [133] 

K-O-NO + (H A N) CI = KCl + 211,0 + ffiNi [134] 

Nitrogen gas has never been condensed to a liquid condition. 
According to Regnault, one litre of nitrogen gas, under standard 
conditions, weighs 1.256167 grammes. It is remarkable for its 
inertness, and one of its chief offices in the atmosphere is to 
moderate the action of its violent associate. The only element- 
ary substances with which it directly combines are boron and 
titanium. Nevertheless, nitrogen has a great capacity for com- 
bination, and is distinguished by the large number and varied 



234 NITROGEN. [§ 159. 

nature of its compounds ; but these can only be formed by in- 
direct methods. 

Oxides of Nitrogen. 

Nitrous Oxide N 2 0, 

Nitric Oxide NO, m 

Nitrous Anhydride N 2 3 , Nitrous Acid H-O-NO, 
Nitric Peroxide N0 2 , v 

Nitric Anhydride N 2 6 , Nitric Acid tf-0 : N0 2 . 

159. Nitric Acid. BN0 3 . — When electrical discharges are 
passed through air which is in contact with caustic or carbo- 
nated alkalies, or when organic matter decays in the atmosphere 
under the same conditions, a partial union of the elements of the 
atmosphere takes place, and nitrates of potassium, sodium, or 
calcium are the usual result. From either of these native ni- 
trates, or nitres, the acid may be obtained. It is usually pre-, 
pared by distillation from a mixture of sodic nitrate (127) and 
sulphuric acid. 

Na-0-N0,+ H,= 0fS0 2 = II,Na=0 2 =S0 2 + II-0-N0 2 . [135] 

One molecule of sulphuric acid is adequate to decompose two 
molecules of nitre; but the temperature required is then much 
higher, and the nitric acid is in part decomposed. The strong- 
est acid thus prepared is a colorless, fuming liquid, boiling at 86° 
and freezing at — 49°. Its Sp. Gr. = 1.552 at 20°. It is un- 
stable, and is partially decomposed when exposed to the light. 

AH-0-N0 2 = 2R 2 + 4N0 2 + O-O. [136] 

The remaining acid is thus diluted, while the nitric peroxide 
colors it yellow. A similar decomposition takes place during 
the distillation of the acid. This decomposition continues until 
the hydrate 2BN0 3 . 3H 2 is formed, which is far more stable 
and distils unchanged at 123°. This is the common strong 
nitric acid of commerce, but it is not a definite compound, the 
composition varying with the pressure under which the acid 
distils. A still weaker acid is much used in the arts under the 
name of aqua-fortis. The strength of the acid may be deter- 
mined from its specific gravity by means of tables prepared for 
the purpose. 



159.] 



NITROGEN. 



235 



Sp. Gr. 

1.500 
1.470 
1.435 



fer uenx. 
HN0 3 


Sp. Gr. 


92.98 


1.395 


82.71 


1.343 


73.10 


1.289 



Per Cent. 
HN0 3 

64.17 

51.50 

45.62 



Sp. Gr. 

1.228 
1.165 
1.105 



Per Cent. 
HN0 3 

36.28 

26.95 

17.62 



Nitric acid is one of the most corrosive agents known. With 
a very few exceptions, it oxidizes all the elementary substances, 
converting them into oxides, acids, or nitrates, as the case may 
be. In these reactions, as a general rule, nitric oxide is evolved; 
but the products vary to a certain extent with the conditions of 
the experiments, and examples will be found under the differ- 
ent elements, and also in [107], [142], [151], and [15G], illus- 
trating the different phases which the reaction may assume. Ni- 
tric acid corrodes all organic tissues, oxidizing them, and forming 
various products, among which the most common are water, 
carbonic acid, and oxalic acid. When more dilute, it stains the 
skin, wool, silk, and other albuminoid bodies of a bright yellow 
color. Very strong nitric acid, when mixed with strong sul- 
phuric acid, acts on some organic compounds in a very remark- 
able way. It removes one or more atoms of hydrogen, and sub- 
stitutes an equal number of atoms of the radical N0 2 in their 
place. (31). 



C C M + H-O-NO, = O,H 5 (N0 2 ) + H 2 0. 

Benzol. Nitro-Benzol. 



[137] 



With the various bases it forms a large class of important salts. 

When the radical is univalent, these salts have the general 

i 
symbol R-0~N0 2 - When the radical is bivalent, the general 

it n 

formula becomes R=0.f(N0 2 ) 2 , or R=OrN i O^ Salts of these 

types are, in the ordinary use of the term, the normal or ortho- 
nitrates ; but, theoretically, nitrogen is capable of fixing five 
univalent radicals, and hence some chemists regard the assumed 
compound H 5 =0 5 =N as orthonitric acid, and salts of that type as 
orthonitrates. By eliminating from this orthoacid first one and 
then two molecules of water, we obtain the following anhydrides, 
the last of which is the ordinary acid. 



Orthonitric Acid 
Metanitric " 
Dimetanitric " 



H-O-NO, 



or H-0-lSrO,.2R 2 0, 
or H-0-N0 2 .B 2 0, 



236 NITROGEN. [§161. 

Salts are known whose symbols may be written on all these 
types, but they may also be written on the ordinary type as 
well. Thus 

ff„BiW 5 iN or Bi=-OiN0. 2 M 2 , 

Dihydro-biainutliic Urihonitrate. Basic bismuthic Nitrate. 

[138] 
3Ig.,\OMNO). 2 or (Mg-0-Mg-0-Mgy0.f(N0 2 ) r 

Muguesie Metanitrate. Trimagnesic Nitrate. 

Such distinctions are of no practical importance, but they are 
of value in pointing out the many-sided relations of our subject 
Under no condition does potassic hydrate form more than one 
salt with nitric acid, and the important theoretical bearing of 
this fact is evident. 

1G0. Nitric Anhydride, N 2 5 , may be obtained by passing 
dry chlorine gas over dried argentic nitrate heated to 95°. 

AAgN0 3 + 2CI-CI = AAgCl + 2N 2 5 + O-O. [139] 

It is a white solid, crystallizing in prisms of the fourth system, 
melting at 29°.o, and boiling at 45°. Very unstable, undergoing 
spontaneous decomposition in a sealed glass tube. By the ac- 
tion of water it forms nitric acid. 

N 2 5 + H 2 = 2HN0 3 . [140] 

161. Nitrous Anhydride. N 2 3 . — Best prepared by the 
action of dilute nitric acid (Sp. Gr. 1.25) on starch. Is also 
formed in the following reactions : — 

As 2 O s + 2HN0 3 = As 2 5 + N 2 3 + H 2 0. [141] 

2Ag-Ag + 6HN0 S = ±AgNO s + N 2 3 + 3H 2 0. [142] 

4 S3"® + (bXD — 2N 2 3 . [143] 

\ 

In each case brownish-red fumes are formed, which, at a low 
temperature, become condensed into a very volatile blue liquid, 
boiling at about 0°. With a small quantity of water it yields 
nitrous acid, H-O-NO, but a large quantity at once decom- 
poses it. 

3iV T 2 <9 3 + H 2 = 4NO + 2HN0 3 . [144] 

If the red vapor is passed into a solution of potassic hydrate, 



§162.] NITKOGEN. 237 

we obtain potassie nitrite, and in a similar way other nitrites 
may be made. 

(2K0H+Aq) + N 2 S = (2K- 0-NO + H a +Aq). [145] 

According to the theory of the last section, ordinary nitrous 
acid is the first anhydride of an assumed acid, H 8 =0 3 =N. This 
would be called orthonitrous acid, and the ordinary acid would 
then be metanitrous acid. The compound Pb 3 i0 6 iN 2 , accord- 
ing to this view, is plumbic orthonitrite, but it may be also re- 
garded as a triplumbic nitrite of the ordinary type (Pb-O-Pb- 
0-Pb)=0 2 =(NO) 2 . 

162. Nitric Peroxide, N0 2 , is best prepared by mixing two 
volumes of nitric oxide with one of oxygen gas, both absolutely 

dry. 

2 EST® + (D<B> = 2Eff®» [146] 

The two gases when mixed immediately combine, yielding a 
deep brownish-red vapor, which, if passed into perfectly dry 
tubes cooled by a freezing mixture, is condensed to a crystalline 
solid. This solid melts at — 9° to an orange-colored liquid, 
which boils at 22°, but when once melted it does not freeze 
even at — 20°. The substance is decomposed by water with 
the greatest readiness. A mere trace of water is sufficient to 
prevent the formation of the crystals, occasioning instead the 
production of a green liquid, which appears to be a solution of 
nitrous anhydride in nitric acid. 

AN0 2 + lf 2 0= 2HN0 3 + N 2 3 . [147] 

If a larger amount of water is present, we obtain nitric oxide 
in place of nitrous anhydride, and the equation becomes 

3N0 2 + H 2 = 2HN0 3 + NO. [148] 

In a similar way, when acted on by metallic hydrates and basic 
anhydrides, it yields a mixture of nitrate and nitrite. Thus 

2K-0-H+ 2N0 2 = K-O-NO + K-O-NO* + H 2 0. [149] 

Nitric peroxide may also be obtained by distilling plumbic 
nitrate, — 

2Pb- 2 =(N0. 2 ) 2 — 2PbO + 4N0 2 + 0=0. [150] 



238 NITROGEN. .[§163. 

Owing to the presence of a little moisture, we first obtain the 
green liquid mentioned above, but towards the end of the pro- 
cess the anhydrous peroxide comes over and may be crystallized. 
Nitric peroxide appears also to be formed in the reaction of 
nitric acid on tin, — 

Sn 5 + 20HNO Z = R l0 O l0 Sn 5 O 5 -f 5E 2 + 20NO 2 ; [151] 

but in this, as in other reactions of nitric acid on the metals, 
the main product is more or less mixed with other oxides of 
nitrogen. 

1 63. Nitric Oxide, NO, is best prepared by the action of 
dilute nitric acid (Sp. Gr. about 1.2) on copper-turnings. 

3 Cu + (SHN0 3 + Aq) = 

(3 Cu(N0 3 ) 2 + iff 2 + Aq) + 2NO. [152] 

The reaction appears to consist, first, in a metathesis of the 
metal with the hydrogen of the acid, and secondly, in the re- 
duction of a further portion of the acid by the hydrogen thus 
liberated. In order to obtain a pure product it is important 
that the acid should be in excess. Nitric oxide may also be 
obtained perfectly pure by heating together a mixture of fer- 
rous chloride, nitre, and hydrochloric acid. 

(QFeCl 2 + 2KNO, + SIICl + Aq) = 

(3[i^ 2 ] C\ + 2KCI -f 477 2 0) + 2NO. [153] 

A mixture of ferrous sulphate, nitre, and dilute sulphuric acid 
(Sp. Gr. 1.18) may also be used. 

Nitric oxide is a colorless permanent gas (Sp. Gr. =s 15), 
but slightly soluble in water (one volume of water dissolves 
one twentieth of a volume of NO). It extinguishes a burning 
candle, but both phosphorus and charcoal, if burning vigorously, 
continue to burn, and with great intensity, when plunged into 
the gas. It is the most stable of the oxides of nitrogen, and is 
not decomposed by a red heat. It is neither an acid nor a basic 
anhydride, but it is marked by its avidity for oxygen, with which 
it forms the brownish-red fumes either of N0 2 or of N 2 O s , ac- 
cording to the proportions present. [143] and [146]. It dis- 
solves freely in a solution of ferrous sulphate, forming a deep 
reddish-brown liquid, from which the gas may be expelled by 



§165.] NITROGEN. 239 

heat. A similar product may be obtained with other ferrous 
salts, and this reaction may be used as a test for nitric acid. 

104. Nitrous Oxide, N 2 0, is best prepared by gently heating 
amnionic nitrate in a glass flask or retort. 

NH A -0-N0 2 == 2H 2 + N 2 0. [154] 

It may also be obtained by exposing nitric oxide gas to the 
action of moistened iron-filings, which absorb one half of the 
oxygen. 

4iVX> —0-0 — 2N 2 0. [155] 

It is also evolved when zinc dissolves in dilute nitric acid, or, 
more surely, when a mixture of equal parts of nitric and sul- 
phuric acids, diluted with eight or ten parts of water, is used for 
dissolving the metal. 

4Zfi + (\0HNO 3 + Aq) — 

(AZn{N0 3 ) 2 + off 2 + Aq) + N 2 0. [156] 

Nitrous oxide is a colorless gas (Sp. Gr. 22), which, by pres- 
sure and cold, may be condensed to a colorless liquid, boiling at 
— 88° and freezing by its own evaporation at about — 101°. 
It is less stable than nitric oxide. It is decomposed by heat, 
and all combustibles burn in it with nearly the same readiness 
and brilliancy as in pure oxygen gas. When pure, it can be in- 
haled without danger, and is much used as an anaesthetic agent. 
With some patients it produces at first a transient intoxication, 
attended at times with uncontrollable laughter. Hence the pop- 
ular name of laughing-gas. It manifests no tendency to unite 
with more oxygen. It is soluble in water to a limited extent, 
and to a much greater degree in alcohol. At 0° one volume of 
water dissolves 1.3 volumes, and one volume of alcohol 4.18 
volumes, of this gas. 

165. Oxychlorides of Nitrogen. — If in reaction [111] no 
gold or other metal is present to unite with the chlorine evolved 
by the aqua-regia, this element combines with the nitric oxide 
set free at the same time, and besides chlorine gas we obtain, as 
products of the reaction, two compounds which we may call ni- 
trous oxychloride and nitric oxydichloride respectively. 

(HN0 3 -f ZHCl + Aq) = 

(2H 2 + Aq) + NO 01 + CI- CI. [157] 



240 NITROGEN, [§166. 

or (2HN0 3 + GIICI + Aq) = 

(\H 2 + M) + 2NOCl 2 + Cl-Cl [158] 

During the early stages of the decomposition of aqua-regia the 
second of the two reactions prevails, and the product is nearly 
pureiVOC^; but as the process advances this becomes more 
and more mixed with NO CI. At the ordinary temperature 
both substances are gases, NO CI having an orange, and NOCl 2 
a deep lemon-yellow color; but by cold they may be readily 
condensed to liquids, which have a red color and resemble each 
other in odor and aspect. They have neither acid nor basic 
relations, but are readily decomposed by chemical agents into 
nitric oxide and chlorine ; and by mixing together these two 
gases the same or similar compounds may be reproduced. By 
the action of dry hydrochloric acid on anhydrous nitric perox- 
ide, still a third compound is formed, which has the symbol 
N0 2 CI, and resembles the other two. The last compound may 
also be obtained by mixing phosphoric oxytrichloride with 
plumbic nitrate. 

SPb=0./(NO 2 ) 2 + 2POCI :i =Pb 3 i0 6 l(PO) 2 +QN0 2 Cl. [159] 

166. Compounds with Hydrogen. — Ammonia Gas. Nff s . 
— Nitrogen and hydrogen gases will not directly combine ; but 
through various indirect methods, not well understood, this 
union is constantly taking place in nature, and ammonia gas is 
the chief product. This gas, or some one of its numerous com- 
pounds, is constantly formed whenever an organic substance 
decays or is charred, as in the process of dry distillation. It is 
also formed in many chemical reactions when nitrogen and hy- 
drogen atoms are brought together at the moment of chemical 
change. Thus when a mixture of nitric oxide and hydrogen 
gas is passed over heated platinum sponge, we have the reaction 

2NO + 511-11= 2H 2 + 2NII S . [1 60] 

So also when nitric acid is added in very small quantities at a 
time to a mixture of zinc and dilute hydrochloric acid, from 
which hydrogen gas is being slowly evolved, we have the re- 
action 

BN0 3 + ±H-H= NH 3 + ZH 2 0. [161] 



§166.] NITROGEN. 241 

But the ammonia thus produced unites at once with the hydro- 
chloric acid present to form ammonic chloride, and in a similar 
way ammonia salts are frequently formed to a limited extent 
when zinc and similar metals are dissolved in nirric acid. Prac- 
tically, we always prepare ammonia gas from the commercial 
ammonic chloride by the reaction 

2NII±Cl + Ca-0.fH 2 —CaCl 2 + 2ff. 2 + 2NH» [162] 

It is a colorless gas, so light (Sp. C3r. 0.591) that it can be 
collected in an inverted bottle by displacement. By pressure 
and cold it may be readily condensed to a liquid, which boils at 
— 38°. 5 and freezes at — 75°. The evaporation of the lique- 
fied gas is attended with great reduction of temperature, and 
this principle is applied in the apparatus of Carre to the artifi- 
cial production of cold. Ammonia has a familiar pungent odor, 
and is useful in medicine as an irritant, but when pure it is 
wholly irrespirable. It is incombustible in air, but burns in an 
atmosphere of oxygen, yielding aqueous vapor and nitrogen gas. 

The composition of ammonia gas may be thus ascertained: 
First, by passing a series of electrical discharges through a 
confined volume of the gas in a eudiometer the volume doubles. 

2NH$ = N*Xr+ 3H-K [163] 

If next we add to this product one half of its volume of oxygen 
gas, then explode the mixture, and subsequently remove with 
pyrogallic acid the residual oxygen, we shall find that the vol- 
ume of nitrogen gas remaining in the tube is exactly one half 
of the volume of the ammonia gas with which we started. Sec- 
ondly, if we shake up in an eudiometer-tube a measured vol- 
ume of chlorine gas with a weak solution of aqua ammonia, 
taking care after the reaction is finished to expel by heat all the 
nitrogen from the liquid, it will be found that the volume of 
chlorine has been replaced by one third of its volume of nitro- 
gen gas. 

With colored test-paper ammonia gas, even when dry, gives 
a strong alkaline reaction, and it directly combines with several 
of the acid anhydrides. These unimportant compounds, however, 
must not be confounded with the important class of ammonia 
salts. In part they correspond to the amides mentioned below, 
11 p 



242 NITROGEN. .[§167. 

but the constitution of others is not well understood. The last 
are frequently called ammonides, and of these sulphuric ammon- 
ide (NH 3 ) 2 . S0 3 , will serve as an example. Ammonia gas 
forms also equally anomalous compounds with many anhydrous 
metallic ^alts. Thus, argentic and calcic chlorides absorb large 
volumes of ammonia gas, forming what appear to be molecular 
compounds, AgCl . 2^iVand GaCl 2 . 8i7 3 iV, in which the am- 
monia seems to play somewhat the same part as water of crys- 
tallization in ordinary salts. But by far the mo>t important 
quality of ammonia is its power of combining directly with 
water and with the acids, as such, to form the large class of 
ammonia salts. In forming these compounds, however, nitro- 
gen changes its quanti valence, and it will therefore be conven- 
ient to class them under a different head. When ammonia gas 
comes in contact with the fumes of a volatile acid, the formation 
of the ammonia salt gives rise to a dense white smoke, which is 
one of the most characteristic tests for this substance. 

167. Amines or Compound Ammonia. — Ammonia gas is 
the type of a large class of compounds, most of them volatile, 
in all of which nitrogen is trivalent. These compounds may be 
regarded as derived from one or more molecules of ammonia 
by replacing the hydrogen atoms either wholly or in part with 
various positive radicals. According as they are fashioned 
after the type of one, two, three, or more molecules of ammonia 
they are called monamines, diamines, &c, and they are distin- 
guished as primary, secondary, or tertiary, according as one, 
two, or three hydrogen atoms in the monamines, or the corre- 
sponding groups of atoms in the polyamines, have been replaced. 
We may represent the type of ammonia either as in (29), or 
more graphically in the vertical form as in table below, which 
contains the symbols of a few of the compound ammonias. 

Monamines. 

Primary. Secondary. Tertiary. 

H) CH 3 ) C 6 tf 5 ) C n H 5 -) CJIJ C II,) 

H>-N HYN H>N CJ-I^N C H b \N C,H h \N 

H) H) H) 'in 'h) c 6 ii 5 ) 

Ammonia. Methylamine. Phenylamine. Diethylamine. Phenylethyl- Methyl ethyl- 
(Aniline.) amine. phenylamine. 



§1G8.]' 



H 

Hi 
Hi 



Primary. 



X 



Ammonia. 
Douoly condensed. 



NITROGEN. 
Diamines. 

% 

Ethylene diamine. 



243 



Tertian). 

Cfi A 

CA 

Diethylene diethyl-diamine. 



: ki iiui if. 



Many of the ammoniated compounds of the metals may be ar- 
ranged under this same type. Thu-, when potassium is heated 
in dry ammonia gas, an olive-green compound is formed, which 
has the composition K,H,II=N; and other examples will be 
given hereafter. 

The amines are all basic, and like ammonia gas combine di- 
rectly with acids to form salts ; but # this character is the less 
strongly marked in proportion as the hydrogen atoms have been 
replaced. The volatile organic bases belong to the same class 
of compounds. 

168. Amides. — The atoms of hydrogen in ammonia gas 
may be replaced by negative as well as by positive radicals; 
but then the product, instead of being basic, is either neutral 
or acid. They are classified and named like the amines, but 
with few exceptions only one or one set of the hydrogen atoms 
can be thus replaced. The following are a few examples: — 



Monamides. 



Diamides. 



C 2 ff 3 
H 
H 



N 



C 7 H 6 0) 
H) 

Benzamide. 



C 2 OA 

H 2 ) 

Oxamide. 



H 2 

Succinamide 



M 



These compounds may also be regarded as formed by the union 
of the compound radical amidogen {H 2 N) with the acid radical, 
and hence the name amides. They differ, then, from the cor- 
responding acids only in containing amidogen in place of hy- 
droxyl. Thus, 



Ho-C 2 H % 0, 

Acetic Acid. 



Carbonic Acid. 



Ho 2 =0 2 2 



Bh 2 =a 4 /r 4 o 2 

Succinic Acid. 



H 2 N-C 2 H z O, {H 2 N) 2 =CO, (H 2 N\ f C 2 2 , (H 2 N\r C A ff,0., 

Acetamide. Carbamide (Urea ?). Oxamide. 



Succinamide. 



2U 



NITROGEK. 



■[§168. 



These amides are all neutral ; but if in the dibasic acids we re- 
place only one of the atoms of hydroxyl, it is evident that we 
shall obtain a class of amides still containing an atom of basic 
hydrogen, and which are, therefore, acids. Thus are formed 



BOM 2 A T =CO. 

Curbaiific Acid. 1 



HO,H a K=C t O„ 

Oxamic Acid. 



HO H.N-C.H^. 

Succinamic Acid. 



Lastly, if we take an acid like lactic acid, H0,H0^C 3 I1 4 0, or 

gly collie acid, HO,HO^C 2 H 2 0, which, although diatomic, is 

only monobasic (43), we can obtain from each acid, at least 

theoretically, two distinct amides, according as we replace the 

+ — 

basic hydrogen (H) or the alcoholic hydrogen (//), see (43). 

The fiivt will be neutral, the second acid; but although several 

of the acid amides are known, the only neutral amide of this class 

which has been investigated is that derived from lactic acid. 



NH.MO-C^O, 

Lactarnide (Neutral). 



HO.NH.f CJIt 0, HO.NHr C, K 2 0. 

Lactarnide (Acid;. Glycolamide (Acid) or OlycocoU. 



From these various amides a large number of compounds 
may be derived by replacing the hydrogen atoms either of the 
amidogen or of the acid with different compound radicals. The 
following are a few examples : — 



C 7 ff 5 

\ N 
H 

Phenyl^benzamide. 



c 6 h 5 



c 2 .o 2 

(C 2 H 5 \}N 2 

Diethyl-oxamide. 



HO-C 2 H,0 

C 7 H 6 

H 

Hippuric Acid. 



HO-C 3 ff 4 0) 
N C 2 H 5 \N 

h) 



Lactethylamide. 



((C 2 ff 6 )0-c 2 o. 2 ) 

Oxamethane. 

(0>H 5 )0-C 5 H 4 
H 

Lactmethane. 



The last two compounds are isomeric, the only difference being 
that in the first the radical ethyl replaces an atom of hydrogen 
of the amidogen, while in the second it replaces the alcoholic 
hydrogen of the lactic acid. That there is a real difference 
between the two is proved by the following reactions : — 

(C 2 tf 5 )0,-C 3 F 4 0> H) 

n>N+K-0-H=K,(C s H & )=O n =C,HtO+H[N lie*] 

H) Potassic Ethyl-lactate. J£J) 

1 The acid has not been isolated, but the amnionic salt is well known. 



§171.] NITROGEN. 245 

HO-C z H A 0) C 2 H 5 ) 

C 2 H.>N + K-0-H==K,H*OfC 3 H i O+ II > N. [165] 

J£ y Potassic Lactate. J J ) 

Ethylamine. 

These complex amide compounds may also be referred to a 
system of mixed types. (Compare 30, Part I.) 

169. Lnides. — If from an acid monamide we eliminate a 
molecule of water, or if from a neutral diamide we eliminate a 
molecule of ammonia gas, we obtain as the product a compound 
which may be regarded as formed by the union of the acid rad- 
ical with the compound radical HJSf. Thus, 

HO,H 2 N= C,ff 4 = H-0-H+ HN- C s ff 4 0. [166] 

Lact-amide. Lact-imide. 

{R 2 N) : rC,H,0 2 = H,N-\- HN-C^Or [167] 

Succiii-amide. Succin-imide. 

Such compounds are called Imides, and they always act as 
monobasic acids. 

170. Nitriles. — If from a neutral monamide we eliminate 
a molecule of water, the residue, which may be regarded as a 
compound of nitrogen with a trivalent radical, has been called 
a Nitrile. Thus, 

JI 2 N- C 2 H z O = H 2 + CM^K [1 68] 

Acetamide. Acetonitrile. 

H 2 N~C 5 ff 9 = H 2 + CA~=K [169] 

Valeramide. Valeronitrile. 

These compounds are weak bases, like ammonia, combining di- 
rectly with acids to form salts, and they may be regarded as a 
part of the class of amines. 

171. Ammonium Compounds. — In all the above compounds 
nitrogen is trivalent, and a single atom of this element, unas- 
sisted, does not appear to be able to hold together more than 
three atoms of hvdrogen or of other univalent positive radicals ; 
but when the different ammonia^ are brought in contact with 
acids, the nitrogen atoms suddenly manifest two additional af- 
finities, and a most important class of compounds is formed, 
in which nitrogen is quinquivalent. The cause of this sudden 
accession of power is not well understood, but it evidently de- 



246 NITROGEN. [§171. 

pends on the reflex influence which the negative atoms or rad- 
icals of the acids exert. In all these cases the ammonias com- 
bine with the acids as a whole, and the reaction is an example 
of synthesis and not of metathesis. The following are a few 
examples : — 

]Sr,H z + HOI = NIH* CI = NH f CI like KCl. [ 1 70] 

Amnionic Chloride. 

mH z +K 1 = mH^(HO) = NH A 0-H like K-O-H. [171] 

Amnionic Hydrate. 

iVW 3 + H-NO, = mH^(NO,) = 

NHfO-NOt like K-O-NO* [172] 

Amnionic Nitrate. 

(2^J3l), + ITfSOt = JSr 2 xff*(S0 4 ) = 

(NH 4 )fOfS0 2 like K 2 =0 2 =S0. 2 . [173] 

Amnionic Sulphate. 

The products thus obtained resemble very closely the salts of 
the alkaline metals. With certain limitations they are suscep- 
tible of the same reactions, and in these reactions the atomic 
group NH± plays the same part as the metallic atoms in the 
other salts. Thus we have 

(Ag-N0 8 + NHfCl + Aq) = 

AgCl+{NH A -NOz + Aq). [174] 

(CaCl 2 + (NffJfOfCO + Aq) = 

Ca=0 2 =CO+ (2NR 4 Cl+Aq). [175] 

Hence we conclude that the ammonia salts are compounds of 
this univalent radical which we call ammonium, and therefore 
we write their symbols as above. But although many attempts 
have been made to obtain the radical substance corresponding 
to NH A , these attempts have been hitherto unsuccessful. It is 
true that when we eleetrolvze a solution of ammonic chloride, 
using as the negative pole of the battery a quantity of mercury, 
we obtain a material resembling a metallic amalgam, which, 
when kept, slowly changes back to metallic mercury, evolving 
a mixture of hydrogen and nitrogen gases ; but it would now 
appear that in this pasty mass the gases are merely mixed, and 
not chemically combined, and, moreover, the total amount of 



§173.] NITROGEN. 247 

material which the mercury thus singularly encloses is exceed- 
ingly small. 

172. Amnionic Chloride (Sal Ammoniac), NH±Cl, is the 
most important of the ammonia salts, and the material from 
which the other ammonia compounds are prepared. It is man- 
ufactured in large quantities from the ammoniacal liquid of the 
gas-works, one of the products of the dry distillation of coal. 
It is a white crystalline salt, very soluble in water, but only 
slightly soluble in alcohol. It sublimes below redness without 
first melting. It is isomorphous with sodic and potassic chlo- 
ride, and resembles these salts, especially the last, very closely. 
Like potassic chloride, it is precipitated from aqueous solutions 
by platinic chloride, wiih which it forms a double salt insoluble 
in water. 

(2NN 4 Cl + PtCl i + Aq) = (NH,Cl) 2 .PtCk+(Aq). [176] 

173. Amnionic Hydrate (Aqua Ammo?iia). (NH^O-H ~\- 
Aq.) — At 0° water absorbs 1,050 times its own volume of am- 
monia gas, but the quantity absorbed rapidly diminishes as the 
temperature rises, so that at 15° it can only hold 727 times its 
volume, and at 24° 600 times its volume. Water saturated at 
15° contains about one third of its weight of ammonia, but in 
consequence of the great expansion which attends the absorp- 
tion, the solution is lighter than water. This solution has the 
pungent odor of ammonia, because the gas slowly escapes even 
at the ordinary temperature of the air, and by prolonged boiling 
the whole may be driven off. In this and in other physical re- 
lations the compound of ammonia with water arts l'ke the solu- 
tion of a gas but in all its chemical relations it behaves like an 
alkaline hydrate. It is strongly caustic ; it precipitates metallic 
hydrates from solutions of their salts, and is very much used in 
the laboratory as an alkaline reagent. It has been called the 
volatile alkali. It differs, however, from the fxed alkalies, soda y 
and potassa, in two important particulars. First, it is decom- 
posed by heat into ammonia gas and water, and is not, therefore, 
properly speaking, volatile. Secondly, it forms with many me- 
tallic radicals soluble double salts, and other compounds of pecu- 
liar constitu'ion. which can have no counterpart- among the com- 
pounds of the alkaline metals. Hence it is that in many im- 
portant particulars the reactions of the ammonia salts are wholly 



248 NITROGEN. [§ 174. 

different from those of the corresponding salts of sodium and 
potassium. They either do not give precipitates under the 
same conditions, or the precipitates obtained have a wholly dif- 
ferent character. Compare [174], [175], with (265), (276), 
and (316). 

174. Amnionic Carbonate. — The commercial salt is & trans- 
lucent white solid, obtained by subliming a mixture of sal-am- 
moniac with chalk. It is very soluble in water, has the odor 
of ammonia, and a strong alkaline reaction. Its composition is 
not unvarying, but the usual product appears to be a mixture 
of hydro-ammonic carbonate and amnionic carbamate (168) in 
equivalent proportions. Exposed to the air it loses about 44 
per cent of its weight, owing to the dissipation of the amnio- 
nic carbamate, which is resolved into C0 2 and NIT 3 , and the 
opaque spongy residue consists of hydro-ammonic carbonate. 
From the commercial salt there may be prepared well-defined 
crystals of the three following compounds : — 

Acid or Hydro-ammonic Carbonate H,NII^0 2 =CO. 
Neutral or Diammonic Carbonate (iV77 4 ) 2 =0 2 =CO . H 2 0. 

Dihydro-tetra amnionic Tricarbonate H 2 (NH i ) i vi 6 vi (CO) 3 . H 2 0. 

A solution of the neutral salt prepared by mixing a solution 
of the commercial substance with the requisite amount of aqua 
ammonia is very much used in the laboratory as a reagent. 

175. Characteristic ^Reactions of the Ammonia Salts. — 
These compounds, when heated with caustic alkalies or alkaline 
earths, give off ammonia gas, which may be recognized by its 
odor, or by the cloud it forms with HCl. The ammonia salts 
are all volatile at a moderate temperature (except in the few 
cases in which the acid is fixed), and are thus readily distin- 
guished from those of the non-volatile bases. This quality is 
of great importance in chemical analysis, and leads us to select 
the ammonia salts, whenever it is possible, as reagents, because 
the excess of the reagent and all the ammoniacal products can 
so readily be eliminated by heat. 

176. Ammonium Bases. — The salts formed by the union 
of the compound ammonias, or amines, with acids, closely re- 
semble those of ammonia, and may be regarded as consisting of 
radicals derived from ammonium by replacing one or more of 
its hydrogen atoms with other positive radicals. Of these com- 



§ 176.] NITROGEN. 2-19 

pounds the most interesting are those corresponding to amnionic 
hydrates, but in which all four of the hydrogen atoms have been 
thus replaced. They may be prepared from the ternary amines 
in a manner which is illustrated by the following reactions : — 

cA Lv+ (cygj)j= |2 r z [177] 

Trietnylamine. KJ -l ±± b J 

Iodide of Tetrathyl-ammonium. 

Ag. 2 + 2 [(CyT,)^-/] + ffiO = 

2A g I+m(C i £r i ) i A T ]:0-H). [178] 

The solutions of the amines in water, although, like aqua 
ammonia, they may be regarded as compounds of an ammo- 
nium radical, are decomposed when evaporated into the volatile 
amine and water, and it might have been anticipated that the 
hydrate of tetrathyl-ammonium would break up in a similar way, 
but such is not the case. This compound is stable, and on 
evaporating the solution resulting from the last reaction the 
hydrate is obtained as a white solid resembling caustic potash. 
It absorbs water and carbonic acid from the air; it precipitates 
the metallic oxides from their salts; it saponifies fats, and it 
neutralizes the strongest acids, just as pota-h does. Several 
similar compounds have been prepared; and since it appears 
that the four hydrogen atoms of ammonium may be replaced 
by the same or by different atoms at will, it is evident that an 
infinite number of such compounds are, theoretically at least, 
possible. These hydrates have a bitter taste, and cannot be 
volatilized without decomposition. In both of these particulars 
they very closely resemble the non-volatile organic alkaloids, 
which are evidently formed after the same type. There are, 
therefore, two classes of bases derived from ammonia; the one 
volatile, after the tvpe of H Z N ; the other non-volatile, after the 
type of NH^O-H; and corresponding to these there are two 
classes of organic alkaloids, the first volatile like nicotine and 
conine, the second non-volatile like quinine and morphine. In 
all these bases the parts are grouped around one or more atoms 
of nitrogen, and the difference between the two c'asses of com- 
pounds depends primarily on the fact that these atoms are tri- 
ll* 



250 PHOSPHORUS. [§ 177. 

valent in the first class and quinquivalent in the second. The 
two classes of compounds are, however, intimately related, and 
may be regarded from different points of view. Thus the 
amides, imides, and nitriles, which we have considered as formed 
after the type of ammonia gas, may al>o be regarded as anhy- 
drides of the salts of the ammonium radicals, and in many cases 
may be prepared from these salts by a simple process of dehy- 
dration. Moreover, careful study will open up many other re- 
lations of these bodies, all of which must be considered before 
we can command a comprehensive view of the sul ject. 

177. Chloride of Nitrogen, NCl s , is a very volatile, yellow, 
oily liquid, obtained by the action of chlorine gas on a strong 
solution of sal-ammoniac. 

178. Bromide of Nitrogen, NBr 3 , is obtained by digesting 
bromide of potassium with chloride of nitrogen, and is similar 
to the last in appearance, but has a much darker color. 

179. Iodide of Nitrogen, N/ 3 , is a black powder, formed 
when aqua ammonia is added in large excess to an alcoholic 
solution of iodine. They are all three highly explosive, and 
illustrate in a most marked manner the instability of all the 
compounds of nitrogen. 

180. PHOSPHORUS. P=31. — Found in nature, chiefly 
in combination with calcium, in calcic phosphate, a mineral sub- 
stance very widely but sparingly disseminated, and an essential 
but subordinate constituent of many plants, and of all the higher 
animal structures. In order to obtain the elementary substance, 
the calcic phosphate (generally bone ashes) is first partially de- 
composed with sulphuric acid. The soluble acid calcic phosphate 
thus obtained is easily separated from the nearly insoluble 
calcic sulphate, by filtration. The solution is then evaporated, 
the acid phosphate mixed with pulverized charcoal, and the 
thoroughly dried mass distilled in earthen retorts. The distil- 
lation proceeds slowly, and requires a very high temperature. 

Ca 3 W,i(PO) 2 + 2HfOfS0. 2 = 

2Ca-0 2 =S0 2 + Hi,CalO & l(PO) 2 . 

Whendried, ff i ,CaW,l(PO) 2 = Ca-0.r(P0. 2 ) 2 -{- 2R 2 0,^ U ^ 

3Ca = 0./(P0 2 ) 2 + C 10 = Ca s W 6 i(PO) 2 + lOCO+P* 

181. Common Phosphorus, P 4 , when perfectly pure, is a 



§182.] PHOSPHORUS. 251 

colorless, transparent solid, but ordinarily it has a yellowish tint, 
and is only translucent. At low temperatures it is brittle, but 
at 20° it is soft like wax. It melts at 45°, and boils at 290°. 
Sp. Gr. of solid 1.83. Insoluble in water, slightly soluble in 
alcohol and ether, still more soluble in both the fixed and vola- 
tile oils, and very soluble in sulphide of' carbon or chloride of 
sulphur. Phosphorus is by far the most combustible of the 
chemical elements. It takes fire below the boiling point of 
water, and slowly combines with the oxygen of the air at the 
ordinary temperature. If in not too small quantity, the heat 
evolved by its slow combustion soon raises the temperature to 
the point of ignition, and it is therefore always preserved under 
water or alcohol. The product of the rapid combustion is 
phosphoric anhydride ; that of the slow combustion in moist 
air chiefly phosphorous acid. Exposed to the air in the dark, 
phosphorus emits a greenish light, and hence its name, from 
cfiws cfiopos ; but this phosphorescence, though always accompany- 
ing the slow combustion, does not appear to be necessarily con- 
nected with it. Sticks of phosphorus, when kept under water, 
become covered after some time with a white crust, which con- 
sists of a mass of microscopic crystals ; and in the course of 
many years these crystals may acquire considerable size. The 
form of the cryslals is the regular dodecahedron of the first sys- 
tem (Fig. 6), and crystals of the same form are obtained by 
slowly evaporating the solution of phosphorus in sulphide of 
carbon. 

182. Bed Phosphortis. — Exposed to the direct sunlight 
under water, phosphorus becomes covered with a red coating, 
and the same red modification is formed in great abundance 
when ordinary phosphorus is heated for several hours to a 
temperature below 235° and 250° in an atmosphere of carbonic 
anhydride, or some other inert gas. Red phosphorus is insol- 
uble in carbonic sulphide, and is thus easily separated from the 
portion which has not been changed. Iodine facilitates the con- 
version, and if a solution of phosphorus in sulphide of carbon, 
containing a little iodine, is sealed up in a glass flask and heated 
for some time to only 100°, red phosphorus is slowly precipi- 
tated. As usually obtained, red phosphorus is an amorphous 
powder; but it has been crystallized, and it appears that the 
crystals are rhombohedrons belonging to the third system. 



252 PHOSPHORUS. [§183- 

Hence phosphorus is dimorphous, and in this respect resembles 
arsenic and antimony. The Sp. Gr. of red phosphorus is about 
2.1. It undergoes no change in dry air, and may even be 
heated to 2.30° without taking fire ; but at a slightly higher 
temperature it changes back to common phosphorus and in- 
flames. The specific heat of red phosphorus is 0.1700, while 
that of the ordinary variety is 0.1387 ; and hence, as we should 
anticipate, this reverse change is attended with the evolution of 
heat. Moreover, the calorific power of common phosphorus is 
to that of red phosphorus in the proportion of 1.15 to 1. In 
general, red phosphorus is less active, chemically, than common 
phosphorus, and is not, like the latter, poisonous. Both varie- 
ties are largely used in the manufcidure of friction-matches. 
The red variety is not used in making the match itself, but 
only in the preparation of the surface on which it is rubbed. 
183. Phosphorus and Oxygen. — The following compounds 
of phosphorus with oxygen, or with both oxygen and hydrogen, 
have been observed: — 

Phosphorous Anhydride P^O^ 

Phosphoric Anhydride P>0& 

Hypophosphorous Acid H-0-(P=0,II z ), 

Phosphorous Acid Hf 2 =(P= 0,H), 

Othophosphoric Acid HfOi(P=0), 

MetMphosphoric Acid H-0-(P=0 2 ), 

Pyrophosphoric Acid ff 4 =0 4 =(P=OfP), 

Sodium salt of Hexabasic Acid N't^O^P^fP^OfP'-OfP), 

Sodium salt of Dodecabasic Acid Na l2 ™ 12 ™(P 10 O VJ ). 

The relations of these compounds will be best understood 
by taking as our first starting-point an assumed compound, 
H 5 =0 6 =P, in which the atoms of phosphorus are united to hy- 
droxy 1 by all their five affinities. Otho 1 and metapho-phoric 
acids are now simply the successive anhydrides of this pent- 
atomic acid. Stalling next from the double molecule of our 
assumed compound, the following anhydrides are possible: — 





Ao x ^o x Ai 


3d. 


H<m(P-=OeP), 


1st. 


// 8 viii0 8 viii(P-0-P), 


4th. 


KfO^PWfP), 


2d. 


ff 6 W<M{P-0. f P), 


5th. 


(PW^P). 



1 The assumed pentatomic acid is by some called orthophosphoric. 



§186.] PHOSPHORUS. 253 

Of these possible compounds the second and fourth are identical 
with ortho and rneta-phosphoric acids, of which the symbols rep- 
resent two molecules, while the third and the fifth are the pyro- 
phosphoric acid and phosphoric anhydride of the above list. 
The first anhydride of this series has not yet been observed. 
In like manner we may take three, four, or more molecules of 
the first compound, and deduce from each of these condensed 
molecules another series of anhydrides ; but of the infinite num- 
ber of compounds thus possible, only the salts of the hexabasic 
and dodecabasic acid mentioned above are known. This scheme, 
however, does not include hypophosphorous and phosphorous 
acids, which have an anomalous constitution. They may be 
regarded as orthophosphoric acids in which atoms of hydroxyl 
(two in the first case and one in the second) have been replaced 
with atoms of hydrogen. The molecules of both acids contain 
three atoms of hydrogen, but the first is only monobasic and $ i 
second dibasic; and this fact illustrates an important principle. 
In all the so-called oxygen salts, only those atoms of hydrogen 
are replaceable by metallic atoms, which are united to the neg- 
ative radical by a vinculum consisting of an equal number of 
oxygen atoms. The hydrogen and oxygen atoms thus paired 
are equivalent to so many atoms of the radical hydroxyl [70]. 
Phosphorous anhydride is the only one of this class of com- 
pounds in which the phosphorus atoms are not quinquivalent. 

184. Phosphoric Anhydride is readily prepared by burning 
phosphorus in dry air. It is an amorphous white powder, hav- 
ing an intense affinity for water, and is sometimes used as an 
hygroscopic agent. It hisses when dropped into water, and 
gives a solution of 

185. Metaphosphoric Acid. — This compound is obtained as 
a vitreous solid (glacial phosphoric acid) by heating orthophos- 
phoric acid to redness. Its solution coagulates albumen, and 
one molecule of the acid saturates only one molecule of sodic 
hydrate. By boiling the solution the acid loses its power of 
coagulating albumen, and acquires greater capacity of satura- 
tion, having changed into 

18G. Orthophosphoric Acid. — This is much the most im- 
portant of these compounds. It is readily prepared by boiling 
phosphorus in not too strong nitric acid, and evaporating the 
liquid product to the consistency of syrup. The ordinary phos- 



254 PHOSPHORUS. [•§ 187. 

phates are all salts of this acid, and one molecule of acid is ca- 
pable of saturating three molecules of base. Many of the phos- 
phates are thus constituted, and these are, theoretically (38), 
the neutral salts ; but evidently we may also have for each base 
two acid salts. Thus in the case of soda we have 

Na^O^PO, H,tfa 2 =-0 3 =-PO, H 2 ,m=O s =-PO; 

so in the case of lime we have 

Ca 3 W 6 i(PO) 2 , H 2 ,Ca 2 lO,%PO) 2 , H A ,CalO,l{PO) 2 . 

Here, as in many other cases, a diatomic metal serves to solder 
together two molecules of the acid. 

187. Common Sodic Phosphate, KNa 2 =0 3 =PO . \^H 2 0, is 
by far the most important of the salts which phosphoric acid 
forms with the bases previou>ly studied. It is, moreover, the 
chief soluble salt of the acid, and is much used in the laboratory 
as a reagent. It is also highly interesting, theoreticallj', be- 
cause it illustrates by its reactions the relations we have just 
been considering. A solution of the salt is neutral to test-paper, 
but when mixed with a solut'on of argentic nitrate, al-o per- 
fectly neutral, we obtain a yellow precipitate of argentic phos- 
phate, Ag 3 E O s E PO, and at the same time the solution becomes 
acid. Heat now the salt to 120°, und it will be found that it loses 
twelve molecules of water ; but when the dried mass is dissolved 
in water, and the solution evaporated, we obtain crystals of the 
same form (rhombic prisms, Fig. 45) and composition as before, 
and which give again the same reaction. But heat the same 
salt to a red heat, and we have a wholly different result. The 
salt has lost thirteen molecules of water; the residue is less 
soluble than before. On evaporation we obtain crystals of a 
different form and composition (Na±P 2 7 . \0H 2 O), and the 
solution, after precipitation with argentic nitrate, although pre- 
viously alkaline, becomes neutral. Moreover, the precipitate, 
instead of being yellow, is white, and has the composition 
Ag 4 P 2 7 . 

188. Microcosmic Salt. H,NH^Na--O^PO . 4i7 2 6>. — If we 
mix together hot saturated solutions of common sodic phosphate 
and sal ammoniac, we obtain the following reaction : — 

(H,Na^O^PO + NH.Gl. AH 2 + Aq) = 

H,NH»Na=-OfPO . 4i7 2 + {Na Gl + Aq). [180] 



§180.] PHOSPHORUS. 255 

As the solution cools, the microcosmic salt crystallizes out, leav- 
ing sodic chloride in solution. This salt, when ignited, loses 
both its water and its ammonia, and the sodic metaphosphate, 
which remains, fuses into a colorless glass at a red heat. This 
glass acts very much like borax, and is used in the same way 
as a blow-pipe flux. 

189. Phosphorus and Hydrogen. — When phosphorus is 
boiled with strong potash or soda lye, or with milk of lime, a 
gas is evolved, called phosphuretted hydrogen, which on com- 
ing in contact with the air inflames spontaneously. This gas 
consists almost entirely of the compound H 3 P ; and when soda is 
used, the reaction by which it is formed is as follows: — ■ 

P 4 + (Sm-0-H+ 3H 2 + Aq) = 

(3J$ r a-0-POIf 2 + Aq) + E 3 P. [181] 

This crude product, however, is not pure H Z P ; for when it is 
passed through a tube cooled by a freezing mixture it deposits 
a small amount of a very volatile yellow liquid, which has been 
found to be a second compound of phosphorus and hydrogen, 
H 4 P 2 , and has the property of inflaming spontaneously to a high 
degree. Moreover, the gas thus treated loses its power of self- 
lighting, and this quality in the crude product is evidently due 
to a small admixture of the liquid substance. When exposed 
to the direct sunlight, the liquid compound gives off R 6 P, and 
deposits a yellow solid, which is a third compound of phospho- 
rus and hydrogen, H 2 P 4 . 

5ff 4 P 2 =±= H 2 P 4 + 6H 3 P. [182] 

This same solid compound is deposited on the sides of the ves- 
sel when the crude product first mentioned is exposed to the 
sunlight, and in this case, also, the gas loses its self-lighting 
power. 

There are, then, three distinct compounds of hydrogen and 
phosphorus. But of these the first is by far the most impor- 
tant, and the other two are chiefly interesting as explaining the 
singular phenomena just noticed. The compound H Z P is the 
analogue of ammonia gas, and differs from it in composition only 
in containing in the place of nitrogen the next lower element 
of the same chemical series. But the differences in properties 



256 PHOSPHORUS. [§190. 

are so great that to superficial observation it would seem as if 
there were no similarity between the two compounds. Thus 
phosphuretted hydrogen is insoluble in water, except to a very 
slight degree, and does not unite with any of the common acids. 
A more careful study, however, discovers very marked resem- 
blances, for it appears that H 3 P does unite with HBr and HI 
to form the compounds (H±P)Br and (H 4 P)I, which resemble 
(H A N)Br and (H A N)L Moreover, the atoms of hydrogen in 
H 3 P may be replaced by methyl, CH 3 , ethyl, C 2 U 5 , and other 
radicals yielding compounds similar to the tertiary amines, which 
we call the phosphines ; and it further appears that the phos- 
phines have a strong basic character, combining with all the 
ordinary acids to form a class of salts corresponding to those of 
the compound ammonias, and yielding also, by reactions similar 
to [177] and [178], compounds analogous to the hydrates of 
the ammonium radicals. There are, however, even here, dif- 
ferences to be noted, — quite important, because they point to a 
tendency in the series which develops into a marked character 
in the next element, arsenic. The compounds trimethylphos- 
phine, (CH 3 ) 3 P, and triethylphosphine, (C 2 H 6 ) 3 P, not only 
combine with acids, but they also unite as diatomic radicals 
either with two atoms of chlorine, bromine, or iodine, or with 
one atom of sulphur or of oxygen. Thus are formed the crys- 
talline compounds 

(C 2 H b ) 3 P-Cl 2 , (ail^P-O, (C 2 H 5 ) 3 P-S. 

Lastly, a compound has been described corresponding to liquid 
phosphuretted hydrogen, and having the symbol (CH 3 ) 2 P- 
(CH 3 ) 2 P, which, like the former, is both liquid and spontane- 
ously inflammable. It has, moreover, the properties of a feeble 
basic radical, and in the chemical series finds its analogue on 
one side in the radical amidogen, and on the other in the re- 
markable compound kakodyl (198). 

190. Phosphorus and Chlorine. — Phosphorus combines 
with chlorine in two proportions. When the phosphorus is in 
excess, phosphorous chloride, PCI 3 , is formed, which is a fuming, 
colorless liquid. When, on the other hand, the chlorine is in 
excess, we obtain phosphoric chloride, PCl 5 , a white crystalline 
solid. Both compounds are decomposed by water, and when 
the water is in large excess the reactions are as follows : — 



§192.] ARSENIC. 257 

PCl 3 + (3E 2 0+Aq) = (Hf0.fPHO + ?>HCl-\- Aq). [183] 

PCl 5 + (4JI 2 + Aq) = (Hf=O^PO + 5HCI + Aq). [184] 

If in the last reaction water is not present in sufficient quantity, 
we obtain quite a different result. 

POl 5 + H 2 = PC1 3 + 2HCL [185] 

The first of the three reactions is important, because it gives 
an easy method of preparing phosphorous acid, and the last has 
a special interest because it illustrates a valuable application of 
phosphoric chloride. This reagent gives us the means of re- 
placing an atom of oxygen with two atoms of chloriffe, and (as 
is illustrated not only by [185], but also by [34]) this simple 
change frequently gives a clew to the molecular constitution of 
a chemical compound. The compound PCl 3 is called phos- 
phoric oxychloride, and there is also a phosphoric sulphochlo- 
ride, PCl 3 S. Both are fuming, colorless liquids. The last, 
when heated with a solution of caustic soda, gives the following 
remarkable reaction : — 

(PCl 3 S + §Na-0-H-\- Aq) = 

{Na^O.^PS + ZNaCl + 2>H 2 + Aq). [186] 

191. ARSENIC. As = 75. — Trivalent or quinquivalent. 
One of the less abundant elements, but in minute quantities 
quite widely distributed. Found native, and in combination 
both with sulphur and with many of the metals. The most 
abundant of the native compounds is Mispickel, FeS 2 . FeAs. 2 , 
and by simply heating this mineral in a closed vessel the ele- 
mentary substance is easily obtained. 

2Fe 2 As 2 S 2 = 4FeS + As 4 . [187] 

It is also prepared by subliming a mixture of arsenious anhy- 
dride and charcoal. 

2As 2 3 + 3 C = As, + 3 00 2 . [188] 

192. "Metallic Arsenic" As 4 , has a bright, steel-gray lustre, 
and conducts electricity with readiness. It is, therefore, fre- 
quently classed among the metals, and hence the trivial name. 

Q 



258 ARSENIC. [§193. 

On the other hand, it is very brittle, and closely allied in all its 
chemical relations to the class of elements with which it is here 
grouped. Arsenic, like phosphorus, is dimorphous, and may 
readily be crystallized both in octahedrons of the first system, 
and in rhombohedrons of the third. Corresponding to these 
two forms are two allotropic modifications, di*tingufehed also by 
differences of density and of other physical qualities, although 
these differences are not so marked as those between the two 
states of phosphorus. In its ordinary condition, arsenic, when 
heated out of contact with the air, begins to volatilize at about 
130° without previously melting, and it cannot be brought into 
the liquid condition except under pressure. The Sp. Gr. of 
the solid is 5.75, and that of the vapor referred to air 10.6. 
Heated in contact with the air, it burns with a pale blue flame, 
and the product of the combustion is arsenious anhydride, As 2 3 . 
It cannot, however, maintain its own combustion, and goes out 
unless the temperature is kept above the point of ignition by 
external means. At the ordinary temperature it rapidly tar- 
nishes in the air, and, when in large bulk, the oxidation is some- 
times sufficiently rapid to ignite the mass. Serious accidents 
have originated from this cause. The burning of arsenic is 
attended with a peculiar odor resembling garlic, which is very 
characteristic. It is insoluble in water or any of the ordinary 
solvents. 

193. Arsenic and Oxygen. — Arsenious Anhydride. As 2 3 . 
— The white powder which is formed by the burning of arsenic 
is the most important and the best known of the compounds of 
this element. It is obtained in very large quantities as a sec- 
ondary product in the roasting of many metallic ores. Like ar- 
senic itself, this compound is dimorphous, and may be obtained 
crystallized both in octahedrons of the first system and in rhom- 
bic prisms of the fourth. Moreover, when freshly sublimed, it 
appears as a vitreous solid, and in this third state it is three 
times more soluble in water than in the crystalline condition. 
Common white arsenic is only sparingly soluble in water, but 
by continuous boiling with water this crystalline condition is 
changed into the vitreous (or colloidal) modification, and a much 
larger amount enters into solution. This change, however, is 
not permanent, and after long standing the excess before dis- 
solved is all deposited in octahedral crystals. When digested 



§194] ARSENIC. 259 

with the mineral acids, or with aqua ammonia, white arsenic 
dissolves still more readily than in water, but on standing, the 
larger part of the As 2 O s is deposited from these solutions in oc- 
tahedral crystals as before, and by evaporation the whole may 
be thus recovered, indicating that no stable compound had been 
formed. 

194. Arsenites. — Arsenious acid, IT 3 =0 3 =As, is only known 
in solution; and indeed there is no evidence that As 2 3 forms 
with water a definite hydrate. There are, however, several 
well-defined arsenites. 

Potassic Arsenite (Fowler's Solution) H 2 ,K=0 3 =As, 

Cupric Arsenite (Scheele's Green) If,Cu=0 3 =As, 

Argentic Arsenite (Brilliant Yellow) Ag^O^As. 

The first is obtained by adding to a solution of caustic potash 
an excess of As 2 3 , and the last two are precipitated when a 
solution of the first is added to the solution of a silver or copper 
salt. Arsenious anhydride is a most violent mineral poison. 
It is also a powerful antiseptic, and is much used in packing 
hides and for preserving anatomical preparations. 

195. Arsenic Acid, H^OfAsO, is readily obtained by treat- 
ing As 2 3 with nitric acid. 

As 2 3 + 2II-0-JV0 2 + 2B 2 = 2IT 3 =-O^AsO + N 2 3 . [189] 

On evaporating the resulting solution under regulated condi- 
tions of temperature, definite hydrates, all white solids, may be 
obtained corresponding to the three conditions of phosphoric 
acid. But they differ from the latter in that when dissolved in 
water they all yield solutions having the same properties and 
containing the same tribasic acid. From this acid a large num- 
ber of arseniates may be prepared. The following, all of which 
may be obtained in well-defined crystals, are isomorphous with 
the corresponding phosphates : — 

Na 3 -=OMsO.UH 2 0, H,Na 2 =-0 3 =-AsO .UH 2 0, f ' 

H 2 ,Na-OMsO . H 2 0, H 2 ,k=-OMsO. L J 

These salts may be all rendered anhydrous by heat, and from 
the acid salts products may be thus obtained corresponding in 



260 ARSENIC. f§196. 

composition to the meta and pyrophosphates ; but when dis- 
solved they reunite with water and become tribasic. Hence 
aqueous solutions of all these arseniates give, with argentic ni- 
trate, the same precipitate, Ag 3 ^0 3 =AsO. This precipitate has 
a brick-red color, and enables us to distinguish an arseniate 
from an arsenite. It is not formed, however, if an excess of 
ammonia or a free acid is present. On adding a solution of 
magnesic sulphate containing an excess of ammonia to a solu- 
tion of an arseniate, a precipitate is obtained, (H A N) v Mg=0^ 
AsO. 6I£ 2 0, which very closely resembles the corresponding 
precipitate obtained with a phosphate under the same conditions. 

106. Arsenic Anhydride, As 2 6 , is obtained as a white 
amorphous solid when arsenic acid is heated nearly to redness. 
At a higher temperature it fuses and is decomposed into As 2 3 
and 0-0. 

197. Arsenic and Hydrogen. — There are two compounds, 
a solid, H±As 2 , and a gas, H 3 As. The gas is formed whenever 
hydrogen, in its nascent condition, comes in contact with a com- 
pound of arsenic, and its formation gives us one of the most 
delicate means of detecting the presence of arsenic in cases of 
poisoning. Thus, when arsenious acid is introduced into an 
apparatus evolving hydrogen, we have the reaction 

JT 3 =-0 8 -=As + SH'ff= ZH 2 + H 3 A$. [191] 

As thus obtained, however, the gas is more or less mixed with 
hydrogen. It may be obtained pure by the following re- 
action : — 

Sn 3 As 2 +(fiHCl+Ag) = (3SnCl 2 + Aq) + 2S^s. [192] 

It is a colorless gas (Sp. Gr. 33.9), which may be condensed to 
a liquid boiling at 30°. It has a repulsive odor, and is exceed- 
ingly poisonous. It burns in the air, forming As 2 3 and H 2 0. 
In the interior of the flame the combustion is imperfect, and 
hence the flame deposits on a cold surface, which is pressed 
upon it, a brilliant mirror of metallic arsenic. The gas is de- 
composed when passed through a red-hot glass tube, and a sim- 
ilar mirror is formed on the inner surface in front of the heated 
portion. By careful experimenting these mirrors may be ob- 
tained with hydrogen gas, which contains only a mere trace of 



§198.] ARSENIC. 261 

arsenic. When arseniuretted hydrogen is passed into a solu- 
tion of argentic nitrate, we obtain the following remarkable 
reaction : — 

H 3 As + ZAg-0-NO* + ±H 2 = 

±Ag 2 + ZH-O-NO, + H 3 =-0 3 =-AsO. [193] 

198. Compounds with the Alcohol Radicals. — Arsenic forms 
compounds analogous to the amines, phosphines, and their de- 
rivatives. The compounds trimethyl-arsine, (CH 3 ) 3 As, and tri- 
ethyl-arsine, ( C 2 H 6 ) 3 As, do not, however, like the corresponding 
phosphines, combine directly with HGl and the similar acids, 
but they do unite very readily with two atoms of chlorine, bro- 
mine, or iodine, or with one atom of oxygen or sulphur, forming 
such compounds as 

(CJf 3 ) 3 As-Cl 2 , (C 2 H 5 ) 3 As=Br 2i (Cff 3 ) 3 As=0, (C 2 H 5 ) 3 As-S. 

They also unite with the iodides and bromides of the alcohol 
radicals, forming such compounds as 

(CH 3 \As-I or {C 2 H^As-Br, 

and from these may be derived basic compounds analogous to 
ammonic hydrate, like 

{CH 3 ),As-0-H or {C 2 H 5 ),As-0-H. 

But by far the most important of this class of compounds are 
those which may be regarded as derived from a remarkable 
radical substance, (CH 3 ) 2 As-(CH 3 ) 2 As, called kakodyl, which 
is formed when a mixture of arsenious anhydride and potassic 
acetate is submitted to distillation in a closed retort. A crude 
complex product is thus obtained, from which the radical sub- 
stance may be subsequently separated. Pure kakodyl is a 
spontaneously inflammable, exceedingly fetid, fuming liquid, 
resembling in many respects the corresponding compound of 
phosphorus. It enters into direct combination with several of 
the elements, and is one of the best defined of the radical sub- 
stances. Representing the group of atoms (CH 3 ) 2 As by Kd, 
the symbols of a few of the more characteristic compounds will 
be as follows : — 



262 AESENIC. [§198. 

Kakodyl Kd-Kd, 

Kakodylous Oxide Kd 2 0, 

Kakodylic Oxide Kd 2 2 , 

Kakodylic Acid H- O-KdO, 

Kakodylic Anhydride ? Kd 2 3 , 

Kakodylous Sulphide Kd 2 S, 

Kakodylic Sulphide Kd. 2 S 2 , 

Sulpho-kakodylic Acid H-S-KdS, 

Sulpho-kakodylic Anhydride Kd 2 S 3 , 

Kakodylous Chloride, Bromide, or Iodide KdCLKdBr, or Kdl, 

Kakodylic Chloride, Bromide, or Iodide Kd Cl 3 , KdBr 3 , or Kdl 3 . 

The mutual relations of the different compounds studied in 
this section are illustrated by the following scheme, which 
includes all the known compounds of arsenic with methyl 
(Me = Clio) and chlorine : — 

Type H 3 N. Type CIH^. 

Me,Me,Me =As, Cl,Me,Me,Me,Me=As, 

Cl,Me,Me'=As, CI, CLMe,Me,MeUs, 

CI Cl,Me~=As, CI CI, Cl,Me,MeUs, 

CI, CI, CI* As, CI, CI, CI, CLMe Us. 

By direct union with Cl 2 , the compounds of the first column 
may be changed into the compounds of the second column on 
the next lower line, and the compounds of the second column, 
when heated, break up into Me CI, and the corresponding com- 
pound of the first column on the same line. Moreover, the 
first compound of the first column unites directly with Me CI to 
form the first compound of the second column. Besides the 
compounds mentioned above, this scheme includes another class 
of compounds, which may be regarded as formed from the rad- 
ical (CH 3 )As (corresponding to HN), not yet isolated. Such 
are 

{CH 3 )As-I 2 , (CH 3 )As=0, 

(CH 3 )As==Cl» Rf0. 2 =((CH 3 )As-0). 

They are called arsenmonomethyl iodide, oxide, &c, and the 
last, arsenmonomethylic acid. It is evident that the atomicity 
of the radical is not the same in all the compounds. 



§203.] ARSENIC. 2G3 

199. Compounds with Chlorine, Bromine, and Iodine. — 
These elements unite directly with arsenic, but only in one 
proportion forming AsCI s , AsBr 3 , and AsT 3 . The first is a 
liquid, the last two are volatile solids at the ordinary tempera- 
ture of the air. They are all decomposed by water. 

2AsBr 3 + 3R 2 = As 2 3 + QHBr. [194] 

200. Compounds with Sulphur. — Arsenic and sulphur may 
be melted together in all proportions. They also form several 
distinct compounds. The most important are 

201. Realgar, As 2 S 2 , a brilliant red solid, much used as a 
pigment, and found in nature well crystallized. ■ 

202. Orpiment, As 2 S s , a brilliant yellow solid, also used as a 
paint. Formed whenever arsenic is precipitated from its solu- 
tions by H 2 S. Also found crystallized in nature. Soluble in 
ammonia and caustic alkalies, and precipitated from such solu- 
tions by acids. 

203. Arsenic Sulphide. As 2 S 5 . — Only known in combination. 
The last two compounds are " sulphur anhydrides," and form 

with the sulphur bases a very large and important class of sul- 
phur salts, many of which are native compounds and important 
metallic ores. The following reactions will illustrate the forma- 
tion of compounds of this class : — 

As 2 S s + (4K-0-H+ Aq) = 

(IT,K 2 -=OMs + H,KfSMs + H 2 + Aq). [195] 

(ff,m 2 =-OMs + 3H 2 S-\-Aq) = 

(E,Na 2 =-S 3 =-As + 2>H 2 + Aq). [196] 





Sulpho-arsenites. 




Proustite, 


Hexagonal 


Ag 3 =S 3 =As, 


Tennantite, 


Isometric 


\_Cu 2 \%SM*2-FeS, 


Sartorite, 


Orthorhombic 


Pb=S 2 -As 2 S 2 , 


Dufrenoysite, 


Orthorhombic 


Pb^SMhS. 



Sulpho-arseniates, 
Enargite, Orthorhombic \_Cu 2 ~] 3 lS & l(AsS).,. 



264 ANTIMONY. [§204. 

These symbols should be compared with those of the corre- 
sponding compounds of antimony, in connection with which 
their mutual relations will be explained. 

204. Characteristic Reactions. — The importance of proving 
the presence or absence of arsenic in cases of suspected poison- 
ing has led to a most careful study of the characteristic reac- 
tions of this element, and hence our knowledge on these points 
is unusually accurate and full. The most striking of these re- 
actions have already been given. Further details or descrip- 
tions of methods by which arsenic, even when in minute quan- 
tities, may be detected and distinguished from antimony lie 
beyond the scope of the present work. 

205. ANTIMONY. Sb = 122. — Trivalent or quinquiva- 
lent. This element is less abundantly distributed than arsenic, 
although found in similar associations. The most abundant na- 
tive compound is the gray sulphide (Antimony Glance), Sb. 2 S 3 , 
which occurs not only in a pure state, but also in combination 
with other metallic sulphides. Antimony is sometimes, although 
rarely, found in the metallic state, and likewise in combination 
with oxygen. 

206. Metallic Antimony, Sb?, is most readily extracted from 
the native sulphide by smelting the ore with metallic iron. 

Sb 2 S 3 + 3Fe = SFeS + Sb 2 . [197] 

It is also extracted by first roasting the ore, 

2Sb. 2 S 3 + 90-0 = 2Sb 2 3 + QS0 21 [198] 

and then melting with charcoal and sodic carbonate. The last 
converts into oxide the small portion of the sulphide which es- 
caped oxidation in the roasting process, 

Sb 2 S 3 + ?>Na 2 -0 2 -CO = Sb 2 3 + 3Na 2 S + 3 00 2 , [199] 

and the charcoal reduces the oxide to metallic antimony, 

Sb 2 3 + 3 C = Sb 2 + 3 CO. [200] 

By oxidizing the crude metal with nitric acid, and again re- 
ducing with charcoal, the antimony may be obtained in a 
pure condition. 



§20G.] ANTIMONY. 265 

Antimony is closely allied to arsenic, but possesses the prop- 
erties of a metal to a still higher degree. It has a bright me- 
tallic lustre, which it preserves in the air. It has a high Sp. 
Gr. (6.7), and conducts heat and electricity with facility. Its 
conducting power, however, is inferior to that of the perfect 
metals, and, moreover, it is very brittle and may be readily re- 
duced to powder. It has also a highly crystalline structure, 
and like arsenic it may be obtained crystallized both in rhom- 
bohedrons of the third system, and in octahedrons of the first. 
The first is the common form, and lumps of the metal may some- 
times be cleaved parallel to the rhombohedral planes, which are 
always more or less evident on the fractured surface. Antimony 
melts at 430°, and it volatilizes, but only very slowly, at a full 
red heat. The melted metal, when heated in the air, slowly ox- 
idizes, and before the blow-pipe it burns, the product of the 
oxidation being in either case Sb 2 3 . Antimony is only very 
slightly acted on by pure hydrochloric acid, even when concen- 
trated and boiling; but on the addition of a very small amount 
of nitric acid the metal dissolves easily, forming a solution of 
SbCl a . 

Sb 2 + (fiHQl -f QHJST0 3 + Aq) = 

(2SbCl 3 + 6ff 2 + Aq) -f 6iV<9 2 . [201] 

With the aid of heat it dissolves in strong sulphuric acid. 

Sb 2 + QR 2 S0 4 = Sb 2 W 6 i(S0 2 ) s + SS0 2 + Qff 2 0. [202] 

Nitric acid, when in excess, converts the metal into a white 
powder insoluble in the acid (chiefly Sb 2 4 ). If, however, the 
nitric acid contains a little hydrochloric acid, the product is 
metantimonic acid. 

Sb 2 + ±H-0-N0 2 =z 

2H-OSb0 2 -\-H a O + ir 2 O s + 2NO. [203] 

Lastly, antimony dissolves readily in a mixture of tartaric 
and nitric acids, which is one of the best solvents of the metal. 
Metallic antimony is chiefly used in the arts to alloy with other 
metals, to which it imparts a greater hardness and durability. 
Type-metal is an alloy of four parts of lead and one of antimony. 
This alloy expands in " setting," and therefore takes a sharp 
12 



266 ANTIMONY. "[§207. 

impression of the mould in which it is cast ; and this property, 
as well as the hardness, renders type-metal peculiarly suitable 
to the important use to which it is applied. Britannia metal, 
an alloy of brass, antimony, tin, and lead, much used as the base 
of plated silver-ware, also owes its hardness and durability to 
the antimony it contains. 

207. Antimony and Chlorine. — Antimonious Chloride. 
SbCl 3 . — A solution of this compound is readily obtained either 
by [201] or by dissolving the native sulphide in hydrochloric 
acid. On evaporating the excess of acid, and distilling the resi- 
due, the chloride is obtained as a white crystalline solid. It is 
deliquescent, very volatile, and melts so readily (72°) that it 
was formerly known as butter of antimony. The Sp. Gr. of 
its vapor, as found by experiment, is 112.7. Antimonious chlo- 
ride may also be obtained by distilling antimony or antimonious 
sulphide with mercuric chloride, and also by distilling a mixture 
of antimonious sulphate with common salt. 

Sb 4 + AffgCl 2 = Sb 2 Hg 2 + lHg. 2 -\Ck + 2^bOl 3 . [204] 

Sb 2 S 3 + ZHgCl 2 = SHgS + 2^b®l 3 . [205] 

Sb 2 W 6 %(S0 2 ) 3 + 6NaCl=3Na 2 =0 2 =S0 2 -f 2SbCl 8 . [206] 

Antimonious chloride is decomposed by water, forming an 
insoluble oxychloride and hydrochloric acid. Hence the solu- 
tion obtained by [201] becomes turbid when diluted with water. 
The presence of tartaric acid in sufficient quantity prevents the 
decomposition, and a solution of this acid dissolves the oxychlo- 
ride when formed. By long-continued washing the oxychloride 
may be converted into antimonious oxide. 

(SbCl s + H 2 G + Aq) = SbOCl + (? HCl + M\ [207] 

2SI)OCl + (H 2 O + Aq) = Sh0 s + (2 HCl + Ag). [208] 

Antimonious chloride combines with the chlorides of the 
metals of the alkalies and of the alkaline earths, and forms sol- 
uble crystalline salts. Hence it may be mixed with concen- 
trated solutions of these chlorides, as also with strong hydro- 
chloric acid, without undergoing decomposition. The following 
are the symbols of a few of these double chlorides, which are 
best regarded as molecular compounds : — 



§209.] ANTIMONY. 267 

&(BJP> CI . SbCl 3 • H^O, 1 2{H,N) CI . SbCl 3 ■ H t O> 

SKCl. SbCl 3i 2KCI. SbCl 3 , 

SNa CI . Sb (7/ 3 , Ba Cl 2 . Sb Cl 3 . 2iff 2 0. 1 

208. Antimonic Chloride, SbCl 5 , may be formed by passing 
chlorine gas over SbCl 3 , or by acting on the metal with an ex- 
cess of the same reagent. It is a volatile, fuming liquid, which 
readily parts with two fifths of its chlorine, and is therefore 
sometimes used, like PCl 5 , as a chloridizing agent. It is at 
once decomposed by water. With only a small quantity it forms 
an oxychloride (compare [185]). 

JI 2 + Sb Cl 5 = 2ECI + Sb Cl s 0. [209] 

With an excess of water, either ortho-antimonic acid or pyro- 
antimonic acid results. 

SbCl 5 + ±H 2 = H^O^SbO + 5HCI, [210] 

or 2SbCl 5 + 1H 2 = H,W^Sb 2 3 + 10HCL [211] 

The presence of tartaric acid prevents these reactions. By 
the action of H 2 S on Sb CI 5 sl sulpho-chloride may be formed. 

SbCl 5 + H 2 S= SbCl s S+2HCL [212] 

A bromide of antimony, SbBr 3 , and an iodide, SbT s , are 
readily formed by the direct action of these elements on the 
metal, but no penta-bromide or iodide has yet been obtained. 
They are both fusible and volatile solids, and when acted on by 
water are converted into SbBrO and SblO. The correspond- 
ing fluoride dissolves in water without decomposition, and forms 
with the alkaline fluorides a number of double salts. 

ZNaF . SbF s , 2 (ff 4 N)F. SbF 3 , KF . SbF 3 . 

209. Antimony and Oxygen. — Antimonious Oxide. Sb 2 3 . 
— This compound, already mentioned as a product of the direct 
oxidation of antimony, may, like As 2 3 , be obtained crystallized 
both in octahedrons of the first system or in rhombic prisms of 
the fourth, and on this difference of form depends the distinc- 

1 These symbols are thus written to show the relations of the compounds. 
To be strictly accurate they should be doubled. 



2G8 ANTIMONY. [§209. 

tion between the two minerals Senarmontite and Valentinite, 
both of which consist of this same substance. The oxide is 
most readily prepared artificially by pouring a solution of SbCl 3 
[201] into a boiling solution of sodic carbonate. 

(3M 2 =0<rCO + 2SbCI 3 + Aq) = 

SM>8 + &M*Cl + Aq) + 3®® 2 . [213] 

Antimonious oxide acts both as a basic and as an acid anhy- 
dride, although the first is by far its most marked character. 
It is but very slightly soluble in water. When the solution of 
SbC/ 3 is poured into a cold solution of sodic carbonate, we 
have the reaction, 

{ZNafOfCO + 2SbC! 3 + H 2 + Aq) = 

2H O &bO + (fiNaCl + Aq) + 30® 2 , [214] 

and the product may be regarded as metantimonious acid, for 
it dissolves in caustic alkalies and forms definite, although very 
unstable, salts. On the other hand, the oxide dissolves in fum- 
ing sulphuric and fuming nitric, as well as in hydrochloric acids, 
forming crystalline salts, in which the antimony plays the part 
of a basic radical. 

The mo*t important salt of this class is that formed by dis- 
solving Sb 2 3 in a solution of acid potassic tartrate (cream of 
tartar). This compound is very much used in medicine as an 
emetic, and hence the trivial name tartar emetic. Tartaric acid 
is tetratomic, but only bibasic (43), and we have the following 
series of compounds : — 

Tartaric Acid H 2 , Hf 0^{ C A H 2 2 ), 

Neutral Potassic Tartrate K 2 , H 2 = =0^( C 4 H 2 2 ), 

Acid Potassic Tartrate X,H, B 2 W 4 ^-( CJ7 2 2 ), 

Tartar Emetic (crystallized) K,Sb , H^ 4 i( C A H 2 2 ) . H 2 0, 
after heating to 200° K,SbW^(C 4 ff 2 2 ). 

It will be noticed that in forming tartar emetic the radical 
SbO of the compound H-O-SbO takes the place of one atom 
of basic hydrogen, which still remains unreplaced in cream of 
tartar. On heating the crystallized salt to 100° it gives up its 



§210.] ANTIMONY. 269 

water of crystallization. At 200° it gives off an additional 
atom of water, formed at the expense of the oxygen in the rad- 
ical just named and of the two atoms of hydrogen distinguished 
as negative in the acid ; and it will be seen that, in the anhydrous 
salt thus obtained, one atom of antimony takes the place of three 
typical atoms of hydrogen in tartaric acid. Compounds similar 
to tartar emetic may be made in a similar way with the oxides 
of arsenic, bismuth, and uranium. Their symbols differ from 
that of tartar emetic only in having the radicals AsO, As0 2 , 
BiO, or UO, in place of SbO, and they undergo a similar de- 
composition when heated. Compounds of the same class may 
also be obtained with other anhydrides than those of the group 
of elements we are now studying (as Fe 2 8 Cr 2 O s , B 2 3 , &c), 
and when it is further added that the potassium in these com- 
pounds may be replaced by other univalent radicals, or even by 
bivalent radicals soldering together two molecules of the ordi- 
nary type, it will be seen that a very large number of such 
salts are possible. Lastly, the fact that a compound has been 
prepared in which two of the typical atoms of hydrogen are 
replaced by the positive radical ethyl, -while the other two are 
replaced by the negative radical acetyl, and the additional fact 
that no salt can be obtained in which all the four atoms are re- 
placed by a well-defined positive radical, give a strong presump- 
tion in favor of the formulas of the tartrates adopted above. 

Antimonious oxide, when heated out of contact with the air, 
volatilizes unchanged, but under the same conditions in the air it 
burns like tinder, forming a higher oxide, Sb 2 4 , which is fixed, 
even at a high red heat. By ignition with charcoal or hydrogen, 
all the oxides are readily reduced to the metallic state. 

210. Antimonic Acid. — The reactions have already been 
given [203], [210], [211] by which the three conditions of this 
acid may be prepared. They are 

Metantimonic Acid H~ OSb 2i 

Orthoantimonic Acid H s =O z =SbO, 

Pyroantimonic Acid J3 4 =O i =Sb 2 O i . 

Pyroantimonic acid may also be prepared by acidifying the 
solution of acid potassic pyroantimoniate mentioned below, 

{H^K^O^Sb 2 0, + 2HCI + Aq) = 

ff 4 W^Sb 2 3 + (2KOI + Aq), [215] 



270 ANTIMONY. [§211. 

but when this precipitate is dried, it loses water and changes 
into metantimonic acid, 

H^O^Sb 2 O s = 2H-OSb0 2 + H 2 0. [216] 

The existence of orthoantimonic acid has not been as yet 
well established, but the other two are well known, and many 
of their salts have been investigated. The most interesting of 
these salts is obtained by fusing antimonic anhydride with an 
excess of potassic hydrate, and extracting the fu^ed mass with 
water. An alkaline solution is obtained, containing a salt 
whose composition is expressed by the symbol H 2 ,K 2 =0± =Sb 2 3 . 
This solution produces a precipitate in solutions of salts of so- 
dium, and is sometimes used as a reagent in testing for this 
element. The sodic salt thus precipitated has the composition 
H 2 ,Na 2 ^0 4 =Sb 2 3 . QH 2 0. Antimonic acid, in either of its con- 
ditions, is insoluble in water, as well as the antimoniates, with 
a few exceptions. In this respect they frequently differ from 
the corresponding compounds of phosphorus and arsenic, which 
they closely resemble in molecular constitution. 

211. Antimonic Anhydride, Sb 2 5 , is readily prepared by 
gently heating metantimonic acid, the product of reaction [203]. 
It is a pale yellow powder, insoluble in water. Fused with al- 
kaline hydrates or carbonates it yields various antimoniates. 
"When ignited alone it gives off one fifth of its oxygen, and the 
product is the same white powder, Sb 2 4 , which is formed by 
the oxidation of antimonious oxide. This intermediate oxide 
is the most stable of the oxides of antimony. It is sometimes 
called antimonious acid, and when fused with the alkalies it 
enters into combination with them, but the products thus ob- 
tained may be regarded as mixtures of an antimonite and an 
antimoniate, and the oxide itself appears to be an antimoniate 
of antimony, SbO~0-Sb0 2 . A rare mineral called Cervantite 
has the same composition. 

212. Antimony and Hydrogen. — Antimoniuretted Hydrogen. 
H 3 Sb. — When any soluble compound of antimony is added to 
an apparatus evolving hydrogen [64], we obtain a product 
closely resembling arseniuretted hydrogen, but containing anti- 
mony instead of arsenic. 

SbCk + 3H-H= H s Sb -f 3HCL [217] 



§213.] ANTIMONY. 271 

The antimony compound thus formed is always mixed with 
much hydrogen gas, and has not yet been obtained in a pure 
condition. When burnt in air it yields water and antimonious 
oxide. 

2H 3 Sb + 30=0=. Sb 2 3 + 3H 2 0. [218] 

If burnt against a cold surface, so that the combustion is incom- 
plete, the antimony is deposited and a metallic mirror is formed. 

4ff a Sb + 3 0=0= Sb, + 6H 2 0. [219] 

The compound is decomposed and a similar mirror formed 
when the gas is passed through a red-hot tube. 

When the gas is transmitted through a solution of argentic 
nitrate we get the reaction 

(3Ag-0-N0 2 + Aq) + H 3 Sb = 

Ag 3 Sb + {3H-0-N0 2 + Aq). [220] 

This reaction, and the well-established trivalent character of 
antimony, fix the composition of antimoniuretted hydrogen be- 
yond all reasonable doubt. 

Compounds of antimony with the alcohol radicals have been 
prepared, both after the type of ammonia and that of the am- 
monium salts. Thus we have 

Trimethyl-stibine (CIT 3 ) 3 Sb, 

Trimethyl-stibine Chloride ( CH 3 ) 3 Sb Cl 2 , 

Trimethyl-stibine Oxide {cH 3 ) 3 SbO, 

Tetramethyl-stibonium Iodide ( CH 3 ) A SbI, 

Tetramethyl-stibonium Hydrate {CH^^Sb-O-H, 

and the corresponding compounds of ethyl and amyl. The re- 
action of triethyl-stibine on hydrochloric acid is interesting, as 
it illustrates the serial relations among the group of elements 
we are studying. (C 2 H 5 ) 3 Sb not only does not combine with 
HCl, but actually decomposes the acid, yielding (C 2 ff 5 ) 3 SbCl 2 
and H~H. Compounds of antimony corresponding to those of 
the kakodyl group are not known. 

213. Antimony and Zinc. — There are two very well marked 
crystalline compounds of antimony and zinc, Zn 3 Sb 2 and Zn 2 Sb 2f 
which give still further evidence of the usual trivalent charac- 



272 ANTIMONY. .[§214. 

ter of antimony. The compound Zn 3 Sb 2 , moreover, decomposes 
water with the evolution of hydrogen gas. 

214. Antimony and Sulphur (Crude Antimony). — Anti- 
monious Sulphide. Sb 2 S 3 . — The gray sulphide of antimony has 
already been noticed as a native product. It is known to min- 
eralogists as Antimony Glance, and is distinguished by its great 
fusibility. Large splinters of the mineral readily melt in a 
candle Mme. Hence it is easily separated by fusion from the 
gangue with which it is found associated, and the process is 
termed " liquation." Its crystals have a bright metallic lustre, 
and the form of rhombic prisms of the fourth system ; but a 
strong tendency to longitudinal cleavage gives to them a bladed 
appearance. 

When antimony and sulphur, or antimonious oxide and sul- 
phur, are melted together in proper proportions, a compound is 
obtained similar to the native sulphide. Moreover, a precipi- 
tate of the same composition falls when H 2 S is passed through 
the solution of any antimonious compound. This precipitate, 
however, has a brick red color, and is probably an isomeric 
modification of the native gray compound. It is insoluble in 
dilute hydrochloric acid when cold, but readily dissolves in the 
hot acid if moderately concentrated. It is also soluble in solu- 
tions of alkaline hydrates. 

Sb 2 S 3 + (<oK-0-H-\- Aq) — 

(KfSfSb + KpQfSb + SR 2 + Aq). [221] 

From this solution it is again precipitated on the addition of an 
acid. 

(KfSfSb + KpOfSb + GHCl + Aq) = 

Sb 2 S 3 + (QKCl -{-311,0 + Aq). [222] 

In like manner it dissolves in solutions of alkaline sulpho- 
hydrates. 

Sb 2 S 3 + (QK-S-H+ Aq) — 

(pX+SfSh + Aq) + SIf 2 S. [223] 

Antimonious sulphide is a strong sulpho-anhydride, and 
many of its salts are important minerals. The following are a 
few examples. We give the symbols in their simplest form, 



§214.] ANTIMONY. 273 

but in the minerals themselves the antimony is frequently more 
or less replaced by arsenic, and the principal metallic radical 
by others isomorphous with it. These compounds are best 
classified by referring them to a series of assumed sulphur acids, 
related to each other like the successive anhydrides of the oxy- 
gen acids (181), but derived from the normal compound of the 
series by eliminating successive molecules of H 2 S. They may 
be distinguished as ortho, meta, and pyro-sulphantimonites, but 
these terms have no special appropriateness except so far as 
they imply a distinction analogous to that which obtains be- 
tween similar oxygen compounds. 

Ortho-sulphantimonites. 

Pyrargyrite Hexagonal Ag^S^Sb, 

Stephanite Orthorhombic Ag 3 =S 3 =Sb . Ag 2 S, 

Polybasite Orthorhombic Ag 3 =S 3 =Sb . 3Ag 2 S, 

Bournonite Orthorhombic ([Cu 2 ~] } Pb 2 )iSQiSb 2 , 

Meneghinite Monoclinic? Pb 3 iS 6 iSb 2 . PbS, 

Tetrahedrite Isometric [ Cu.^SqeS^ . ZnS. 

Meta-sulphantimonites. 

Miargyrite Monoclinic Ag-S~SbS, 

Zinkenite Orthorhombic Pb=S./Sb 2 S 2 , 

Chalcostibite Orthorhombic Cu=S.fSb 2 S 2 , 

Berthierite Fe-S 2 -Sb 2 S 2 . 

Pyro-sulphantimonites. 

Jamesonite (feather ore) Orthorhombic Pb 2 =S 4 =Sb 2 S, 

Freieslebenite Monoclinic 3Ag w xS 10 *Sb 4 S . 4Pb 5 *S 10 *Sb 4 S. 

A few points in connection with the above formulae require 
further explanation. Of the three dyad atoms which compose 
the basic radical of the mineral Bournonite, two are atoms of 
lead, and one a double atom (34) of copper. Now we may either 
suppose that each molecule of the mineral is constituted as our 
symbol would indicate, or we may regard it as a molecular 
aggregate of two distinct compounds, namely, [ Cu 2 ~} 3 lS^Sb 2 
and Pb 3 lS§lSb 2 , and as containing for every two molecules 
12* R 



274 ANTIMONY. {§214. 

of the last one molecule of the first. In Freieslebenite, how- 
ever, the proportions of silver and lead are such that the com- 
position of the mineral can only be accurately expressed in the 
second of the two ways just indicated, and this is the general 
rule in the mineral kingdom. Again, the minerals Stephanite, 
Polybasite, Meneghinite, and Tetrahedrite may be best regarded 
as molecular aggregates of an ortho-sulphantimonite and a sim- 
ple metallic sulphide, in which the la?t plays very much the 
same part as the water of crystallization in our ordinary salts. 
In all the above cases the results of anal}>is would indicate 
a great constancy in the relative number of heterogeneous mole- 
cules which enter into the composition of the mineral ; but in 
other cases no such constancy is observed, and one element is 
found replacing another in almost any proportion. In tetra- 
hedrite, for example, we frequently find the copper more or less 
replaced by silver or mercury, the antimony in like manner re- 
placed by arsenic or bismuth, and the zinc by iron. This we 
express by writing the symbols of the replacing elements to- 
gether within the same brackets. Thus \_\_Cu 2 ~\,Ag 2 ,Hg~\ stands 
for only one atom, but indicates that in the mineral the copper 
is more or less replaced by silver and mercury. So also the 
symbol \_Zn,Fe~\ represents only one atom, but indicates that 
the zinc is to a certain extent replaced by iron. In its most 
general form the symbol of tetrahedrite would be written, — 

[[Ou 2 lAg 2 tfg^S<M[Sb,As,Bq 2 . [Zn,Fe]S. 

This symbol indicates nothing in regard to the relative propor- 
tions of the elements enclosed in the same brackets, and in fact 
this proportion is variable in different specimens of the same 
mineral, but it does show that, so far as the number of atoms is 
concerned, [[ Cu 2 \Ag 2 ,Hg~\ : [Sb.As,Bi] : [Zn,Fe~] = 3:2:1. 

It is, of course, impossible, according to our present theories, 
that each molecule should have this complex constitution ; but 
we may suppose that in the mineral there are certain molecules 
containing one set of elements, and other molecules a different 
set, the actual specimen being an aggregate of all ; and further, 
we must suppose that there are two kinds of molecular aggre- 
gation, one in which the molecules are united in more or less 
definite proportions, and a second where they are merely mixed 
in any proportions which accident may have determined. 



§217.] BISMUTH. 275 

215. Antimonic Sulphide. Sb 2 S 5 . — When H 2 S is passed 
through a solution of SbCl 5 , an orange-colored precipitate is 
formed, having the composition which our symbol indicates** 
It may be questioned, however, whether the precipitate is not 
an intimate mixture of Sb 2 S 3 and S=S,. for when treated with 
sulphide of carbon two fifths of the sulphur is dissolved, Sb 2 S s 
being left ; and, moreover, it is decomposed by boiling hydro- 
chloric acid into SbCl 3 , JI 2 >S, and S=S. On the other hand, it is 
dissolved in alkaline hydrates and sulphides, forming sulphanti- 
moniates, and from these solutions the same substance is again 
precipitated on the addition of an acid. 

4Sb 2 S, + (2AK-0-H+ Aq) = 

{3K 3 -=0 3 =-SbO + SJfcSfSbS + \2H 2 -f Aq). [224] 

Sba/Ss + (ZK 2 S+Aq) = (2K 3 -=S 3 -=SbS + Aq). [225] 

(2K 3 ~=S 3 =-SbS + §HCl + Aq) = 

Sb 2 S 5 + (6KCI + Aq) + Sff a S. [226] 

216. Characteristic Reactions. — The formation of the red 
sulphide by the action of H 2 S is one of the most characteristic 
indications of the presence of antimony; but, before this test 
can be applied, the antimony must be separated from all those 
elements which would obscure the reaction, by the well-known 
methods of qualitative analysis. The blow-pipe reactions of 
antimony are also very characteristic. They consist in the for- 
mation of a brittle metallic bead or a coating of volatile oxide 
on charcoal, and in the peculiar bluish-green color which this 
oxide imparts to the blow-pipe flame. 

217. BISMUTH. ^' = 210. — Trivalent and quinquivalent. 
One of the rarer elements. Usually found native, sometimes 
combined with sulphur, in bismuth glance, Bi 2 S 3 , and rarely 
with both sulphur and tellurium, in tetradymite, Bi 2 Te. 2 S. Me- 
tallic bismuth is readily extracted from the native mineral by 
fusion (liquation). After the analogy of phosphorus and ar- 
senic, we assign to the elementary substance the molecular for- 
mula Bi 4 ; but since the metal does not volatilize except at a 
very high temperature, we have not been able to determine its 
molecular weight experimentally. Bismuth melts at 265°, and 
forms alloys which are remarkable for their great fusibility. 



276 BISMUTH. - [§218. 

An alloy containing' two part9 of bismuth, one of lead, and one 
of tin, melts at about 94 a , and the addition of cadmium reduces 
the melting-point still lower. These alloys expand on hard- 
ening, and are, therefore, useful for making casts. 

As we descend in the series from antimony to bismuth, the 
metallic qualities become still more marked. The Sp. Gr. of 
bismuth equals 9.83. Its lustre is brilliant, with a reddish 
tinge. It is less brittle than antimony, and even is slightly 
malleable. Bismuth' may readily be crystallized in rhombohe- 
drop.s isomor'phous with those of antimony; but it has not yet 
been crystallized in forms of the isometric system. Bismuth is 
not dissolved by strong hydrochloric acid, nor even by sulphuric 
acid, except when concentrated and boiling. Nitric acid read- 
ily dissolves it with evolution of N0 2 , forming a well-crystal- 
lized nitrate (distinction from antimony). The metal al>o dis- 
solves in aqua-regia, and combines directly with chlorine, bro- 
mine, and iodine. 

218. Bismuth and the Alcohol Radicals. — No compound of 
bismuth and hydrogen is known, but bismuth combines with 
ethyl, forming a xery unstable liquid, which inflames spontane- 
ously in the air and explodes at 150°. It has the composition 
(0 2 ff & ) 3 Bi, and from it may be obtained the compound ( C 2 II 5 ) 3 
Bll 2 in yellow six-sided crystalline plates. This is the iodide 
of a bivalent radical, which forms also definite but very unsta- 
ble compounds with chlorine and oxygen, and is capable of 
replacing the hydrogen of nitric or sulphuric acids. 

219. Bismuth and Chlorine. — Only one compound of bis- 
muth and chlorine is known, BlCl 3J and this may be obtained 
either by passing chlorine over the metal, by distilling the metal 
with corrosive sublimate, or by distilling the residue obtained 
when a solution of the metal in aqua-regia is evaporated to dry- 
ness. The product in either case is a very fusible and volatile 
solid resembling the corresponding compound of antimony. It 
dissolves in hydroehloric acid, but is decomposed by water into 
hydrochloric acid and insoluble oxychloride of bismuth, BIO CI. 
The same oxychloride is precipitated when a solution of bismu- 
thous nitrate is poured into a solution of common salt. It is a 
brilliant white powder, known under the name of pearl white, 
and much used as a cosmetic. It is insoluble in tartaric acid, 
ammonic sulphide, or solution of potash, and is thus distinguished 



§220.] BISMUTH. 277 

from oxychloride of antimony precipitated under similar condi- 
tions. Bismuthous chloride combines with hydrochloric acid 
and the alkaline chlorides to form double salts, and, like SbOl^ 
may be mixed with concentrated solutions of these compounds 
without undergoing decomposition. 

The compounds of bismuth with bromine, iodine, and fluorine 
are BiBr 8 , BIL, and BJFl* 

220. Bismuth and Oxf/f/en. — Metallic bismuth does not 
tarnish in the air, but at a red heat the melted metal slowly 
oxidizes, and before the compound blow-pipe it burns brilliantly. 
The product of the oxidation is Bismuthous Oxide, BL z O%. The 
same compound is obtained by heating the nitrate to a low red 
beat. It is a pale yellow powder, which melts at a full red heat 
to a dark yellow liquid. It is insoluble in water, and will not 
directly combine with it; but by pouring a solution of bismu- 
thous nitrate in dilute nitric acid into dilute aqua ammonia, or 
into a solution of potassic hydrate, a white hydrate of the metal 
is precipitated. This hydrate, when dried, has the composition 
BiO-O-H; but there are reasons for believing that the precip- 
itate falls of the composition Bi*Q&H& By a gentle heat, or 
by boiling with caustic alkalies, all the water is expelled and 
JliJh is left. Bismuthous oxide is a decided basic anhydride. 
It is dissolved by hydrochloric, nitric, and sulphuric acids, form- 
ing definite salts. Nevertheless, by fusing the oxide with sodic 
carbonate, an unstable compound is obtained, in which the 
metal is the basic radical {Na~0-BiO). 

By passing chlorine through a solution of K-OH, holding 
/i/'./lj in suspension, a red deposit is obtained, which is a mix- 
ture of bismuthic acid, IIO-Bi0 2 , and bismuthic anhydride, 
Bt 2 5 . 

BnO z -f {1K-0-H+ 2CI-CI + Aq) = 

e 2ff-OBW 2 + (±KCl + H 2 + Aq). [227] 

The two products may be separated by means of cold nitric 
acid, which dissolves only the anhydride. Bismuthic acid dis- 
solves in a solution of potassic hydrate, giving a blood-red solu- 
tion ; but the salt thus formed is, very unstable and is decom- 
posed by mere washing. The other compounds of the acid are 
little known. At a temperature of 130° the red-colored acid is 
resolved into water and the brown anhydride. 



278 BISMUTH. " [§221. 

Bisrauthic anhydride, when gently heated, changes into an in- 
termediate oxide, Bi 2 0±, or rather into a mixture of this oxide 
and Bi 2 3 . If heated in a current of hydrogen, it is at once 
completely reduced to the lower degree of oxidation. When 
heated with sulphuric or nitric acids it evolves oxygen, produ- 
cing bismuthous sulphate or nitrate ; and when heated with hy- 
drochloric acid it evolves chlorine, yielding bi-muthous chloride. 

221. Bismuthous Nitrate, Bi=0 3 =(N0 2 ) s . hH 2 0, is the most 
important of the salts of bismuth. It forms large deliquescent 
crystals. It readily dissolves in water strongly acidified with 
nitric acid, but when mixed with a large volume of water it is 
decomposed, and a white basic salt of somewhat variable compo- 
sition, formerly called the magistery of bismuth, is precipitated. 
The first precipitate appears to consist mainly of the compound 
Bi=0 3 E (N0 2 ),B 2 ; but this is more or less decomposed by the 
subsequent washings. The product is now generally known as 
the basic nitrate of bismuth, and is used medicinally. 

222. Bismuthous Sulphate. — When bismuihous oxide dis- 
solves in sulphuric acid, the normal sulphate Bi 2 =0 & l{S0 2 ) 3 is 
undoubtedly formed; but when the solution is evaporated this 
salt lo^es the larger part of its acid, and the yellow product 
obtained, when the residue is gently heated, has, approximately 
at least, the composition (BiO) 2 =0 2 =S0 2 ; although, being easily 
decomposed by heat, it is difficult to obtain the compound in a 
pure condition. The formula of the basic nitrate may also be 
written BiO~0-N0 2 . H 2 0, and the formation of salts of this 
type is characteristic of the class of elements we are studying. 

223. Bismuth and Sulphur. — The native compound of bis- 
muth and sulphur already mentioned, Bi 2 S 3 , is isomorphous with 
antimony glance, Sb 2 S 3 < which it closely resembles. The same 
compound may be obtained by fusing bismuth with sulphur in 
proper proportions, and also by passing H 2 S through the solu- 
tion of a bismuth salt. The precipitated sulphide is black, and 
is not dissolved by alkaline hydrates or sulpho-hydrates. It is 
also insoluble in all the dilute mineral acids, but it dissolves in 
hot nitric acid. When, however, the solution is mixed with 
water, most of the bismuth is again precipitated as basic nitrate. 
When heated in the air, Bi 2 S 3 is oxidized and yields S0 2 and 
Bi 2 3 , which melts to dark yellow globules. Bismuthous sul- 
phide is a sulpho-anhydride, and the following minerals may be 
regarded as sulpho-bismuthites : — 



§224.] QUESTIONS AND PROBLEMS, 279 

Kobellite Orthorhombic ? P\lS^lBi,Sb, 

Needle Ore " (lGu^Pb 2 )lS Q %Bi 2 , 

Wittichenite " [ Cu^lS^Bi^ 

Emplectite " [ Cu 2 ] =S 2 =Bi 2 S 2 . 

224. Characteristic Reactions. — The decomposition of the 
soluble salts of bismuth by water, with the formation of an in- 
soluble basic salt, is the most characteristic reaction of this 
metal. The salts of bismuth are easily reduced on charcoal 
before the blow-pipe, and yield a metallic bead, surrounded by 
a yellow coating of oxide. 



Questions and Problems. 
Nitrogen. 

1. In order to determine the composition of the air, 863.7 c. m. 3 
of air measured under a pressure of 55.76 c. m., and at 5°. 5, were 
mixed in an eudiometer-tube with a quantity of pure hydrogen. 
After addition of hydrogen the volume measured 1006.7 c. w. 8 , 
under pressure of 69.11 cm. The mixture was next exploded 
by an electric spark, and after the explosion the residual gas 
measured 800.7 c. m. 3 , under a pressure of 49.14 c. m., and at 5°. 6. 
Required composition of air by volume in 100 parts. 

Solution. By [4] and [9] it will be found that the three volumes 
given above would have measured, under the normal condi- 
tions, respectively 621 20, 897.38, and 507.38. The absorption 
due to the combustion of the hydrogen is then 897.3 — 507.3 
= 390 eTnT 3 Of this \ or 130 was oxygen. Hence 621.20 
crm. 3 of air contained 130 cTnT. 3 of oxygen and 491.2 cTin. 3 
of nitrogen, or 100 parts contained 20.92 oxygen and 79.08 
nitrogen. 

2. In another experiment 885.4 cTnT. 3 of air at 53.88 c. m., and 
0°.5 were taken. After addition of hydrogen, volume measured 
1052.7 c. in. 3 , at 70 31 c. m. and 0°.5. After explosion th^ volume 
was reduced to 858.3 cTm: 3 , at 51.36 c. m. and 0°.5. Required 
composition of air by volume in 100 parts. 

Ans. Oxygen 20.93, nitrogen 79.07. 

3. One cubic metre of dry air, measured under normal conditions, 
was passed over ignited copper-turnings. How much must the 
copper have increased in weight? Ans. 299.9 grammes. 

4. In preparing nitrogen gas by [132], what volume of nitrogen 
is obtained for every litre of chlorine used ? Ans. £ of a litre. 



280 QUESTIONS AND PEOBLEMS. 

5. What weight of nitric acid, Sp. Gr. — 1.47, can be made from 
170 kilos, of soda nitre, and what weight of sulphuric acid must be 
used in the process ? [135.] 

Ans. 196 kilos, of sulphuric acid, 152.4 nitric acid. 

6. When, in the preparation of nitric acid, two molecules of nitre 
are used to each molecule of sulphuric acid, one half of the nitric 
acid is given off with great readiness ; but to obtain the second half 
we must heat the materials to a much higher temperature. In the 
first stage of the reaction sodic bisulphate is formed, and in the 
second, neutral sodic sulphate. Write the two successive reactions. 

7. How much sulphuric acid is required for the decomposition of 
303.3 grammes of potassic nitrate ? Ans. 294 grammes. 

8. Write the reaction of nitric acid on sulphur, assuming that 
the products are sulphuric acid and nitric oxide. 

9. Write the reaction of nitric acid on copper, assuming that the 
products are cupric nitrate and nitric oxide. 

10. How much nitric acid (Sp. Gr. 1.228) is required to dissolve 
14.7 grammes of copper ? Ans. 107.6 grammes. 

11. How much to dissolve 16.7 grammes cupric oxide ? 

Ans. 73.21 grammes. 

12. A quantity of plumbic nitrate, weighing 0.993 grammes, yields 
on ignition 0.669 gramme of plumbic oxide. By another determi- 
nation it appears that 1.324 grammes of the same salt, ignited in a 
glass tube with copper-turnings, yield 89.34 cTUT 3 of nitrogen. 
Deduce the percentage composition and symbol of nitric acid, 
assuming that the composition of plumbic oxide and the atomic 
weight of lead, oxygen, and nitrogen are known. What reason have 
you for assuming that the acid molecule contains only one atom of 
hydrogen ? 

13. Write the reaction of nitric acid on phosphorus, assuming 
that phosphoric acid and one or more of the oxides of nitrogen are 
the products of the reaction. 

14. Write the reaction of nitric acid on cotton. (31.) 

15. Illustrate by means of a table the relations of the various 
acids and anhydrides which may be theoretically derived from 
orthonitric acid. 

16. In nitric acid and the nitrates, what is the quantivalence of 
nitrogen ? 

1 7. In nitrous acid and the nitrites, what is the quantivalence of 
nitrogen ? 



QUESTIONS AND PKOBLEMS. 281 

18. Illustrate by means of a table the relations of the various 
acids and anhydrides which may be theoretically derived from 
orthonitrous acids. 

19. Can nitrite ever be isomeric with a nitrate ? What is the 
essential difference between the two classes of compounds ? 

20. The £}p. (B>t". °f nitric peroxide vapor referred to air has 
been found to be 1.72. How does this value agree with the number 
deduced from theory ? 

21. With what volumes of oxygen gas must one litre of nitric 
oxide be mixed, to prepare respectively nitrous anhydride and 
nitric peroxide ? 

22. The Sp. Gr. of nitric peroxide would feem to compel us to 
assign to the compound the symbol we have adopted, and the same 
group of atoms also constantly acts as a univalent radical. Can 
you harmonize these facts with the theory of (69) ? 

23. What volume of oxygen is required to convert 3 grammes of 
nitric oxide (in presence of water) into nitric acid ? 

Ans. 1674.6 cTnT. 3 

24. Write the reaction of nitric peroxide on calcic hydrate. 

25. In the preparation of nitric oxide by [152], why should you 
anticipate" that nitrous oxide, or even nitrogen gas might be evolved, 
when the nitiic acid was nearly exhausted ? 

2G. Analyze the reaction [152], and represent the two stages by 
separate equations. 

27. Analyze the reaction [153], and determine the amounts of the 
different factors which should be used in order to make 10 litres of 
nitric oxide gas. • 

28. Write the reaction when ferrous sulphate, sulphuric acid, and 
nitre are heated together. 

29. The Qn. (*5r. o£ nitric oxide referred to air is 1.038. How 
does this compare with the theoretical number ? 

30. When sodium is heated in a confined quantity of NO, the 
volume of the gas is reduced to one half, and the residue is found 
to be pure nitrogen. Assuming that the Sp. Gr. is known, show 
that this fact proves that the symbol we have assigned to the com- 
pound must be correct. 

31. Analyze reaction [154], and show in what it differs from [133]. 

32. What weight and what volume of nitrous oxide can be ob- 
tained from 240 grammes of ammonic nitrate ? 

Ans. 132 grammes, or 66.9 litres. 



282 QUESTIONS AND PROBLEMS. 

33. One litre of nitric oxide gas will yield by [155] what volume 
of nitrous oxide ? Ans. ^ litre. 

34. Analyze reaction [156], and represent the two stages by sep- 
arate equations. 

35. What evidence is given that nitrous oxide is less stable than 
nitric oxide ? 

36. When sodium is heated in nitrous oxide no change of volume 
results, and the residue is pure nitrogen. The Sp. Gr. of nitrous 
oxide is 22. Deduce from these facts the symbol of the compound. 

37. What volume of gas would a litre of nitrous oxide yield when 
decomposed by heat ? Ans. 1^ litres. 

38. What is the quantivalence of nitrogen in nitrous oxide, and 
what in nitric oxide ? 

39. What are the relations of the oxychlorides of nitrogen to the 
oxides ? 

40. What strong reason may be adduced for doubling the formula 
of nitric oxydichloride ? Would not the same principle require us 
to double the symbols of two of the oxides ? and what argument 
can you urge in favor of the symbols adopted in this book ? 

41. What is the specific gravity of ammonia gas referred to air, 
and referred to hydrogen ? Ans. 0.591, and 8.5. 

42. What would be the volume of 3.0464 grammes of ammonia 
gas at 273°.2 and 38 c. m. ? Ans. 16 litres. 

43. What weight of ammonia would be obtained from one litre 
of NO by reaction [160] ? Ans. 0.7614 grammes. 

44. Ammonia gas may also be formed by the action of metallic 
zinc (when in contact with platinum or iron) on a mixture of a 
nitrate wiih a solution of potash. Write the reaction [16l]. 

45. In order to determine the amount of nitric acid present in a 
specimen of crude so la nitre, 1.000 gramme was treated as in the 
last reaction. The ammonia evolved was conducted into a solution 
of hydrochloric acid, and subsequently precipitated with platinic 
chloride. This precipitate weighed 2.1017 grammes. What was the 
per cent of pure soda nitre ? Ans. 80%. 

46. In order to obtain 10 litres of ammonia gas, how many 
grammes of sal ammoniac must be taken ? Ans. 23.96. 

47. What volume of nitrogen would be formed by burning one 
litre of ammonia ? Wr.te the reaction. Ans. \ litre. 

48. When an organic substance is heated with soda lime (a mix- 



QUESTIONS AND PROBLEMS. 283 

ture of caustic soda and lime), all the nitrogen present is evolved as 
ammonia, which may be collected in hydrochloric acid and com- 
bined with platinic chloride as above. In a given determination 
the weight of the precipitate thus obtained was 2.232 grammes. 
What was the weight of nitrogen in the compound ? 

Ans. 0.140 grammes. 

49. Deduce from the results of the eudiometric experiments de- 
scribed on page 241 the symbol of ammonia gas. Must we know 
the specific gravity in order to fix the formula definitely ? 

50. Show that the result of the experiment with chlorine gas 
confirms the formula just deduced. 

51. Write the symbols of the different amines according to the 
plan of (29). 

52. The amides may be derived from the corresponding acids 
through what replacement ? 

53. After what two types may the symbols of the amides be 
written ? 

54. Write the symbols of oxamic and succinamic acids after the 
water type. 

55. Explain the meaning of the terms basic and alcoholic, as 
applied to the atoms of hydrogen. 

56. Write the symbols of the two lactamides after the ammonia 
type. 

57. How may the imide and nitrile compounds be regarded as 
constituted on the type of ammonia ? 

58. The nitriles (170) may be regarded as cyanides of what 
radicals ? 

59. Why shouM you anticipate that the imide compounds would 
have an acid, and the nitrile compounds a basic character? 

60. Write the reactions which take place when acetic, benzoic, 
lactic, and oxalic acids combine with ammonia. 

61. Write the reactions corresponding to [174 and 175], using the 
sodium instead of the ammonium salts. 

62. What proof do you have that ammonium is a univalent rad- 
ical? 

63. What per cent of NH S does the platinum salt contain ? 

64. When aqua ammonia is added to a solution of ferrio chloride, 
(Fe„)Cl 6 , ferric hydrate, (Fe 2 )Ho 6 , is precipitated. Write the re- 
action. 



284 QUESTIONS AND PEOBLEMS. 

65. Write two reactions in which aqua ammonia acts like a solu- 
tion of caustic soda, and two others in which it does not. 

66. Write the reaction which takes place when a mixture of am- 
nionic chluride with calcic carbonate is sublimed. 

6 7. Write the reaction by which the sublimed carbonate when 
exposed to the air changes to the acid carbonate. 

68. When a solution of ammonic chloride is boiled with a solution 
of caustic soda, ammonia gas is evolved. Write the reaction. 

69. Write the symbols of the compounds formed by the union of 
the amines described in (167), both with hydrochloric acid and with 
water. 

70. Write the symbol of the ammonium base which contains the 
radicals phenyl, C G Z/ 5 , amyl, C b H lv ethyl, C 2 H 5 , and methyl, CII r 

71. Show what different compounds may be formed by the dehy- 
dration of the acetate, lactate, and oxalate of ammonia. 

Phosphorus* 

72. The Sp. Gr. of phosphorus vapor has been observed to be 
63.8, and a<cording to Deville no material change is effected by a 
temperature of 1,040°. Moreover, the specific gravities of the va- 
pors of the following compounds have been determined, and also 
the per cent of phosphorus which they contain. 

„ „ Per cent of 

&p. ur. Phosphorus. 

Phosphuretted Hydrogen, 17.1 91.18 

Phosphorous Chloride, 68.4 22 55 

Phosphoric Oxychloride, 76.6 20.19 

Given these results of observation, show how the atomic weight of 
phosphorus and the molecular constitution of the elementary sub- 
stance may be determined. 

73. The atomic weight of phosphorus, now received, was found 
by burning a known weight of red phosphorus in perfectly dry air, 
and weighing the phosphoric anhydride thus formed. Assuming 
that one gramme of phosphorus yields 2.2903 grammes of phosphoric 
anhydride, what must be the atomic weight of phosphorus? How 
far does this experiment modify the conclusion reached in the last 
problem ? 

74. How much phosphorus can be obtained from 9.3 k^os. of pure 
calcic phosphate by [179] ? Ans. 1.24 kilos. 

75. Can you discover any connection between the difivr^nce of 
specific heat of the two varieties of phosphorus, and the difference 



QUESTIONS AND PROBLEMS 285 

of calorific power ? Does the first difference wholly explain the 
last? 

76. Show that ortho- and meta-phosphoric acid may be derived 
from the assumed pentatouiic acid by successive dehydration, and 
make a table which shall exhibit the different possible derivatives 
of this compound. 

77. Takino- orthophosphoric acid as the starting-point, in place of 
the assumed pentatomic aeid, show how the different varieties of 
phosphoric aeid may be deduced. 

78. What is the basicity of phosphorous and hypophosphorous 
acids ? and what is the quantivalence of phosphorus in these com- 
pounds ? 

79. When either phosphorous or hypophosphorous acids are heat- 
ed, they break up into orthophosphoric acid and PH Z . Write the 
reaction in each case. 

80. Compare together the nitrates and phosphates of the univa- 
lent and bivalent metallic radicals. 

81. Write the reaction of a solution of argentic nitrate on a 
solution of common sodic phosphate, and show why, after precipita- 
tion, the solution must be acid. 

82. Write the reaction which takes place when common sodic 
phosphate is heated to redness. 

83. Write the reaction of a solution of argentic nitrate on a solu- 
tion of sodic pyrophosphate. If the first salt is used in excess, why 
must the solution after the precipitation be neutral ? 

84. Pyrophosphoric acid may be prepared by first adding plum- 
bic acetate to a solution of sodic pyrophosphate, when plumbic 
pyrophosphate is precipitated, and then decomposing this precipi- 
tate suspended in water with H 2 S. The solution thus obtained 
evaporated in vacuo gives crystals of the compound. Write the 
reactions. Why may not the solution be evaporated by heat in the 
usual way ? 

85. Write the reaction which takes place when PH 3 burns. 

86. Write the symbols of Trimethyl-phosphine ; Tetramethyl- 
phosphonium Hydrate ; Trimethyl-amyl-phosphonium Iodide. 

87. Write the symbols of the platinum and gold salts of tetra- 
ethyl-phosphonium. (136) (147). 

88. Write the symbols of Triethyl-phosphine Oxide and Triethyl- 
phosphine Iodide. How does the last differ from Triethyl-phospho- 
nium Iodide ? 



286 QUESTIONS AND PROBLEMS. 

89. Explain the use of PCl 5 as a reagent, and give illustrations 
of its peculiar action. 

90. Can you devise a method by which the reaction [183] may 
be applied in the preparation of phosphorous acid V 

91. Does the reaction [186] throw any light on the constitution 
of phosphoric acid ? 

92. What different degrees of quantivalence does phosphorus 
manii'est iu the compounds described above ? Point out the ex- 
amples of each condition. 

93. Mdke a summary of the resemblances and differences be- 
tween the compounds of nitrogen and those of phosphorus. 

Arsenic. 

94. Represent by graphic symbols the constitution of Mispickel, 
and show how it is possible that the double atoin of sulphur should 
replace the double atom of arsenic. 

95. What should be theoretically the specific gravity of arsenic 
vapor releired to air ? Aus. 10.4. 

96. Compare together the formulas of nitrous and arsenious acids, 
and point out their relations to each other. Is phosphorous acid 
allied to the other two ? 

97. Write the reactions by which cupric and argentic arsenites 
are formed. 

98. Write the symbols of the three hydrates of arsenic acid, and 
give their names, following the analogy of phosphoric acid. 

99. If the arseniates [190] are heated until all the water is 
expelled, what will be the symbols of the compounds left ? 

100. Write the react-on of argentic nitrate on a solution of either 
of the compounds. [190.] 

101. Write the reaction of a solution of magnesic sulphate and 
ammonia on a solution of either of the compounds. [190.] 

102. State the differences between phosphoric and arsenic acids. 

103. Write the reaction which takes place when H 3 As burns, 
both with a sufficient and with a limited supply of oxygen. 

104. How may the reactions described in (197) be used to detect 
the presence of arsenic in a suspected liquid ? 

105. How could you discover the presence of the arsenic acid 
formed by reaction [193]? 






QUESTIONS AND PROBLEMS. 287 

106. State the resemblances and differences between the amines, 
the phosphines, and the arsines. 

107. Is the quantivalence of arsenic the same in all the com- 
pounds of kakodvl ? 

108. .In what respects does kakodyl resemble, and in what does 
it differ irom, the corresponding compound of phosphorus ? 

109. Does the relation of arsenic to chlorine differ materially 
from the relation of phosphorus to the same element ? 

110. Write the reaction of H 2 S on a solution of As 2 3 in dilute 
hydrochloric acid. 

111. Analyze the reactions [195] and [196], and give the names 
of the products which are formed. 

112. What would be the chemical names of the minerals Prous- 
tite and Enargite, and what are the corresponding oxygen com- 
pounds ? Define the class of compounds to which these minerals 
belong. 

Antimony. 

113. Why is the molecular weight of antimony doubtful ? 

114. Theoretically, what weight of metallic antimony should be 
obtained from 1,020 kilos, of antimony glance ? Ans. 732 kilos. 

115. The most common impurities of commercial antimony are 
arsenic, iron, copper, and lead. Why should the process described 
(206) tend to remove these substances ? 

116. Write the reaction when antimony burns. 

117. Write the reaction of nitric acid on antimony, assuming 
that the products<are Sk 2 O i and NO. 

118. Write the reaction of hydrochloric acid on Sb 2 S 3 . What 
will prevent the resulting solution from becoming turbid when 
mixed with water ? 

119. What should be theoretically the Sp. Gr. of SbCl 3 f 

120. Why is it probable that the double chlorides (207) are 
molecular compounds ? 

121. When SbCl 3 is mixed with strong HCl -f- Aq, what com- 
pound would analogy lead us to suppose is formed in the solution ? 

122. Write the reaction of chlorine gas (in excess) on antimony 
and on SbCl 3 . 

123. Write the reaction of water on SbBr 3 and Sbl r 



288 QUESTIONS AND PROBLEMS. 

124. Write the reactions -when Sb 2 3 dissolves in HCl-\- Aq and 
H 2 SO,. [202.] 

125. Write the reaction when Sb 2 O s dissolves in cream of tartar. 

126. Write the reaction when tartar emetic is heated to 200°. 

127. Write the symbols of the compounds formed by dissolving 
As 2 3 , A$ 2 & , or Bi 2 0^ in cream of tartar. 

128. Write the symbols of the compounds of the same class 
derived from FejO v Cr 2 3 , and B 2 3 , assuming that the radicals 
Fe 2 2 , Ci\O v and BO replace the SbO of tartar emetic. 

129. Write the reaction when to a solution of tartar emetic is 
added a solution of calcic chloride, knowing that the corresponding 
lime compound, being insoluble, is precipitated. Calcium, it must 
be remembered, takes the place of two atoms of potassium. 

130. Write the symbol of diaceto-diethylic tartrate. 

131. State the grounds for the distinction between the three sets 
of hydrogen atoms which tartaric acid contains. By what names 
do you distinguish the different sets of atoms, and what other ex- 
amples have been studied in which a similar distinction has been 
made ? 

132. What is the name of the compound H o ,K^0=S\0J 
Write the reaction of a solution of this reagent upon a solution 
of Na CI 

133. On boiling its solution, the acid potassic pyroantimoniate 
changes into a metantimoniate which does not precipitate soda. 
Write the reaction. 

134. Write the reaction of (HCl-\-Aq) on Zn 3 Sb 2 , assuming 
that the product is H. 6 Sb. 

135. Write the symbols of the ethyl and amyl compounds of 
antimony, following the analogy of the methyl compounds whose 
symbols are given. 

136. Write the reaction of triethyl-stibine on hydrochloric acid. 

137. Represent by graphic symbols the constitution of Zn s Sb 2 
and Zn 2 Sb 2 , and give the symbols of other compounds formed after 
the same type. 

138. Write the reaction when antimonious oxide and sulphur are 
melted together. 

139. Write the reaction when H 2 S is passed through a solution of 
tartar emetic. 

140. Analyze reactions [221], [222], and [223], and name the 
classes of compounds to which the several products belong. 



QUESTIONS AND PROBLEMS. 289 

141. Show by symbols the relations of the assumed sulphur acids 
to which the several sulphantimonites are referred. 

142. Explain the distinction between a chenrcal compound and 
a molecular aggregate. What different orders of combination do 
the facts and the atomic theory require of us to assume in such a 
mineral as Tetrahedrite ? 

143. How are the phenomena of isomorphous substitution in the 
mineral kingdom to be explained in harmony with the atomic 
theory ? 

144. Write the reaction of H 2 S on a solution of SbCl 5 . 

145. Write the reaction of hydrochloric acid on the precipitate 
obtained by the last reaction. 

Bismuth. 

146. Represent by graphic symbols the constitution of Bismuth 
Glance, and Tetradymite. 

14 7. Compare the qualities of metallic bismuth with those of the 
other elementary substances belonging to the same series, consider- 
ing especially the crystalline form and the specific gravity. 

148. Write the reaction of nitric acid on bismuth, and compare 
this reaction with that of nitric acid on antimony. 

149. Write the reaction of aqua-regia on bismuth. 

150. Compare the compounds of the alcohol radicals with the 
different members of the nitrogen series of elements, and present 
the subject in a written form. 

151. Write the different reactions by which BiCl 3 may be formed. 

152. Write the reaction of water on BiCl 3 , and the reaction 
when a solution of bismuthous nitrate is poured into a solution of 
common salt. 

153. Why does the presence of a large amount of H^NCl prevent 
a solution of BiCl 3 from becoming turbid when mixed with water? 

154. Compare BiCl z with the corresponding chlorides of the same 
series. What inference do you draw from the fact that the com- 
pound BiCl b has not been obtained ? Have any other facts been 
mentioned pointing to the same conclusion ? What is the evidence 
that bismuth is ever quinquivalent ? 

155. Write the reaction when bismuth burns, or is more slowly 
oxidized. 

156. Write the reaction when bismuthous nitrate is heated to a 

13 s 



290 QUESTIONS AND PROBLEMS. 

low red heat. Why in this process is it important to avoid a higher 
temperature ? 

157. Write the reaction when a solution of blsmuthous nitrate 
(in dilute nitric acid) is poured into a solution of putassic hydrate. 

158. Write the reactions when bismuthous oxide dissolves in 
hydrochloric, nitric, or sulphuric acid. 

159. Compare the oxides and hydrates of the elements of the 
nitrogen series, and, by tabulating their symbols, show that their 
molecular constitution is analogous. Trace also the variation in 
their properties as vou descend in the series. 

160. Write the reaction of water on bismuthous nitrate, assum- 
ing that the basic salt whose symbol is given above, together with 
free nitric acid, are the resulting products. 

161. If Bl 2 S 3 and Sb 2 S 3 are precipitated together, how may the 
two be separated ? 

162. Write the reaction when Bi 2 S 3 is roasted in a current of air. 

163. To which of the three classes of salts, distinguished on page 
273, must the several sulpho-bismuthites be referred V 

164. Compare the sulpho-salts of bismuth, antimony, and arsenic, 
and point out their mutual relations. 



Division IX. 

225. VANADIUM. V== 51.21. — Trivalent and quinqui- 
valent. A very rare element, discovered in 1830 in the iron 
ores of Taberg in Sweden. It has since been found associated 
with the iron and uranium ores of other localities, and more 
recently it has been found in considerable quantities in certain 
remarkable metalliferous sandstone beds occurring in the county 
of Cheshire in England. Vanadium is also the essential con- 
stituent of a few very rare minerals. Of these the most impor- 
tant is Vanadinite, which is a vanadate of lead, and so closely 
resembles the native phosphate and arseniate of the same metal 
as to leave no doubt that all three have a similar molecular con- 
stitution, and hence that vanadium is a perissad element like 
phosphorus and arsenic. Thus we have the following minerals, 
which are all isomorphous with each other : — 

Apatite (Ca 5 F)*0 9 *(PO) 3 , 

Pyromorphite (Pb b 01) * 9 ™{PO) 3 , 






§225.] VANADIUM. 201 

Mimetine (P?> 5 CI) « 2 *(As 0) 3 , 

Vanadinite (Pb 6 CI) « 9 i*( VO%. 

The study of the other compounds of vanadium leads to the 
same conclusion, and shows that the same character already no- 
ticed in Bismuth and Antimony is developed in this element to 
a still higher degree. The lowest oxide of vanadium, VO, is a 
powerful univalent or trivalent radical, and combines with chlo- 
rine or replaces hydrogen like an elementary substance, and 
almost all of the compounds of the element, formerly known, 
and which can be directly prepared from the native vanadates, 
are compounds of this radical, now called vanadyl, but which 
was for a long time mistaken for the element itself. We have, 
for example, (VO)Cl 3 ,a yellow fuming volatile liquid boiling 
at 12G°7 with Sp. G>\ = 1.84 and Sp. Gr. = 88.2, also 
( VO) Cl 2 in brilliant green tubular crystals, next ( VO) CI, a 
light brown powder, and lastly, (VO) 2 Cl, a brownish yellow 
powder resembling mosaic gold. The true chlorides of vana- 
dium can only be prepared from the metal or its nitride, and. 
the air must be carefully excluded during the process. The 
following have been recently described by Roscoe : VCJ 2 , a 
bright apple green, solid in hexagonal plates, with a micacious 
lustre ; VCl 3 , in brilliant tubular crystals with color of peach 
blossoms ; and VCI A , a dark reddish-brown volatile liquid, boil- 
ing at 154°, with Sp. Gr. at 0°= 1.858 and Sp. Gr. = 93.3. 
Roscoe was unable to obtain the pentad compound. 

The oxides of vanadium are, — first, V 2 2 or VO-VO, ob- 
tained as a gray metallic powder when the vapor of VOCl 3 
mixed with hydrogen is passed over red-hot carbon. It dis- 
solves in dilute acids with the evolution of hydrogen, and can- 
not be deprived of its oxygen except with the greatest difficulty. 
Secondly, V 2 3 , obtained as a black powder when V 2 5 is re- 
duced by hydrogen at a red heat. Jt is insoluble in acids. 
Thirdly, V 2 A , obtained in the form of blue shining crystals by 
allowing V 2 3 to absorb oxygen from the air. Fourthly, V 2 5i 
vanadic anhydride, a brownish-red crystalline solid, fusible at a 
red heat, and sparingly soluble in water. The solution has a 
yellow color, and is strongly acid ; but no definite hydrate has 
been described. Vanadic anhydride dissolves in concentrated 
sulphuric acid when boiling, giving a dark red solution. If 
this is diluted with fifty times its volume of water, and heated 
with metallic zinc, it rapidly changes color, passing through all 



292 VANADIUM, [§225. 

shades of blue and green until it attains a permanent lavender 
tint. To each of these shades corresponds a certain degree of 
oxidation of the dissolved vanadium, thus bright blue to V 2 4 , 
green to V 2 3 , and lavender to V 2 2 ; and by using less active 
reducing agents the change may be arrested at any desired 
point. The lavender solution absorbs oxygen with such avidity 
as "" to bleach indigo and other vegetable coloring matters as 
quickly as chlorine, and far more powerfully than any other 
known agent/' 

From vanadic anhydride we derive the vanadates, of which 
there appear to be three classes corresponding to the phosphates. 

1. Metavanadates as in NH^O V0 2 or P^O.f ( V0 2 ) 2 . 

Dechenite. 

2. Pyrovanadates as in JStafOf V 2 3 or Pb.fOf{ V 2 8 ) 2 . 

Deacioizite. 

3. Orthovanadates as in NafO.fVO . 16ff 2 or Ca s vi O/\ V0) 2 . 

Of these salts the metavanadates are the most and the ortho- 
vanadates the least stable, the reverse of what is true in the 
case of the phosphates. 

There are two nitrides of vanadium, VN and VN 2 . The 
first is a black powder obtained by acting on ( VO) Cl 3 with dry 
NH Z . Its composition has been determined by analysis, and it 
is interesting not only as fixing the atomic weight of the metal, 
but also as the starting-point from which the true chlorides 
of vanadium, and the metal itself, have been reached. 

Metallic vanadium has been obtained by reducing VC1 2 with 
hydrogen. It is a light whitish-gray powder, which under the 
microscope appears as a brilliant crystalline metallic mass with 
a silver-white lustre. This metallic powder has a Sp. Gr. = 
5.5, and is not magnetic. It does not volatilize or fuse when 
heated to redness in an atmosphere of hydrogen. It does not 
tarn^h in the air or decompose water at the ordinary tempera- 
tures, but when thrown into a flame it burns with brilliant scin- 
tillations. It does not dissolve in hydrochloric acid hot or cold, 
and only slowly in hot sulphuric acid, but nitric acid of all 
strengths attacks it with violence. It is not acted upon by 
solutions of the caustic alkalies, but when fused with sodic 
hydrate hydrogen gas is evolved and a vanadate formed. It 
Unites directly with chlorine gas to form VCl 4 , and with nitro- 
gen gas to form VN, and it is capahle of absorbing as much as 



§226.] URANIUM. 293 

1.3 per cent of hydrogen gas. It attacks all glass and porce- 
lain in which it is heated, a compound of silicon and the metal 
being formed. It yields also an alloy with platinum, and for 
these reasons, as well as on account of its very great avidity 
(when heated) for both oxygen and nitrogen, it has been one of 
the most difficult of all the elements to isolate. 



Division X, 

22G. URANIUM. U= 120. — One of the rarer elements. 
Always found in nature combined with oxygen, chiefly in 
Pitchblende, which is essentially the compound U 3 0^ and in 
a rare mineral called Uranite. Of the last there are two vari- 
eties : the first is a phosphate of uranium and calcium, and 
the second a phosphate of uranium and copper. 

<7a,(£70) 4 I0 a l(P0) 2 .8# 2 or ta,(£70) 4 10 6 l(P0) 2 . 8J7 2 0. 

In many of its chemical characteristics, uranium very closely 
resembles vanadium. Like the last element, it forms an oxide, 

UO, which acts as a univalent radical, replacing hydrogen and 
combining directly with chlorine ; and all the most important 
stable and characteristic compounds of uranium may be re- 
garded as compounds of this radical. Moreover, U 2 2 , like 

F 2 2 , cannot be decomposed by the ordinary reducing agents, 
and was formerly mistaken for the metal itself. Uranyl acts 
both as a basic and as an acid radical. Of the uranyl com- 
pounds, the most important, besides the native phosphates al- 
ready mentioned, are Uranyl Chloride, ( UO) CI, Uranyl Fluor- 
ide, (UO)F, Uranyl Hydrate, {UO)-0~H (a yellow powder), 
Uranyl Nitrate, {UO)-0-N0 2 .SH 2 (a beautiful yellow salt, 
crystallizing in long striated prisms), and Uranyl-potassic Sul- 
phate, K,{UC) = 2 =S0 2 . H 2 0; and to these may be added a 
number of remarkable double salts, which may be formed by 
the union both of the chloride and the fluoride of uranyl with 
the chlorides or fluorides of the metals, of the alkalies, or earths. 
Indeed, these double salts are a characteristic feature of ura- 
nium, and one which becomes still more marked in the next 
element, Columbium. 



294 UBAH1U1E ' [§226. 

If to a solution of a uranyl salt we add ammonia, or the so- 
lution of any other alkali or earth, we obtain a yellow precipi- 
tate. This is not, however, as might have been expected, the 
hydrate of uranyl, but a compound of the radical with the alkali, 
in which uranyl acts as an acid radical. The constitution of 
these compounds is not well understood, but they are probably 
mixtures of uranyl hydrate with a compound of the form 
R-Q-{ UO). The so-called yellow uranium oxide of commerce 
is a hydrate thus prepared, retaining about two per cent of am- 
monia. Ad these uranyl compounds have a yellow color, and 
the yellow oxide is used to communicate a beautiful and pecu- 
liar yellow to glass. Glass thus colored, and the transparent 
uranyl salts, are to a high degree fluorescent. 

Judging from the uranyl compounds alone, we should con- 
clude that uranium was a peris-ad closely allied to vanadium 
and the nitrogen group of elements; but there are other com- 
pounds of uranium which do not readily conform to this theory. 
Thus we have a chloride, UC/ 2 , and a series of tiranaus salts 
(all having a green color), in which one atom of the metal ap- 
pears to combine with two atoms of chlorine, or to replace two 
atoms of hydrogen. These would seem, on the other hand, to 
indicate that uranium was an artiad element allied to iron ; and 
the important fact that the native oxide. c7 3 4 , is isomorphous 
with the magnetic oxide of iron sustains this view. Uranium 
thu- appears to stand between the nitrogen group of elements 
of the peri-sad family and the iron group of the artiad family. 
It belongs in a measure to both, and its compounds may be in- 
terpreted according to the one or the other plan of molecular 
grouping. In classing it with the peris-ad.- we merely follow 
what appear to be its normal relations ; but others may reason- 
ably entertain a different view, and further investigation is re- 
quired to determine its quantivalence. Uranium thus illustrates 
very forcibly the remarks already made on chemical classifi- 
cation. (103.) 

Of metallic uranium hut little is known, It has been ob- 
tained by decomposing the chloride UCI 2 with potassium, and 
appears to be a steel-white metal (Sp. Gr. = 1S.4), which is 
slightly malleable, and not readily oxidized by atmospheric 
agents. If heated, however, it burns in the air, and dissolves 
in dilute acids with the evolution of hydrogen. The compounds 



§226.] QUESTIONS AND PROBLEMS. 2'Jo 

of uranium have found but few applications in the arts. The 
"yellow oxide" is used, as already stated, for coloring glass, 
and the so-called black oxide (U A O r ), obtained by igniting the 
nitrate, is employed as a black pigment in painting on porcelain. 
The nitrate, which is the most common soluble :-alt, has been 
thought to have feoine valuable qualities in photography. 



Questions and Problems. 

1. State the grounds on which the conclusion in regard to the 
atomicity of vanadium is based, and represent by .graphic symbol 
the constitution of Vanadinite. 

2. How does the Sp. Gr. of the vapor of vanadic oxytrichloride 
compare wiih the theoretical value? 

3. It has been shown by careful analysis that the above chloride 
contains 61.276 per cent of chlorine. What is the atomic weight 
of vanadyl, and what that of vanadium? Ans. 6 7.29, and 51.29. 

4. In order to determine the atomic weight of vanadium from 
vanadic anhydride, Roscoe reduced V z O h by hydrogen to vanadic 
oxide, V 2 O z . Four experiments gave the following results : — 



1st, 
2d, 


Weight of V 2 0--ased. 
7.739 7 grammes, 
6 5819 " 


Weight of F 2 0, obtained. 
6.3*27 grammes. 
5.4296 " " 


3d, 


5.1895 " 


4.2*19 " 


4th, 


5.0450 " 


4.1614 " 



Deduce the atomic weight of vanadium. 

5. Berz<-lius assigned to Vanadir- Anhvdride the symbol VO,. and 
to Vanadyl Chloride the symbol VCl r On this hypothesis he found 
for the atomic weight of vanadium, by the method of the last prob- 
lem, the value 137 (when 0= 16)." which would be redm-ed to 
134.74 by the more accurate determinations of Roscoe. S'ate the 
reasons for believing that the true atom'c weight of the element is 
51.21, and that the compounds have the symbol* aligned to them 
above. Show how far these conclusions have been proved, and 
point out the cause of the former error. 

6. State the grounds for classing uranium with vanadium, as well 
as the reasons which might be urged for associating it with iron, and 
write the rational symbols of the uranium compounds on the as- 
sumption that this element is an artiad. 



296 COLUMBIUM. §227.] 



Division XL 

227. COLUMBIUM (Niobium). Cb = 94. — Pentad. 
This element forms the acid radical of Pyrochlore, Columbite, 
Samarskite, Euxenite, Aeschynite, Fergusonite, and a few 
otlier rare minerals. They are all compounds of columbic 
anhydride, Cb 2 5 , with various metallic oxides, — among 
which those of cerium, yttrium, and their associated elements 
are especially to be distinguished. The columbium, however, 
is almost invariably replaced to a greater or less extent by tan- 
talum. Columbite, the most abundant of these minerals, has 
the symbol [Fe,Mny0 2 =([_ Cb,Ta] 2 ) 2 . It has a black color, a 
submetallic lustre, and a specific gravity from 5.4 to 6.5, in- 
creasing as the proportion of tantalum increases. When finely 
powdered it is easily decomposed by fusion with potassic bisul- 
phate, and on subsequently boiling the fused mass with water 
a white insoluble residue is obtained, which consists chiefly of 
Cb 2 5 , and from this the different compounds of columbium 
may be prepared. Of these the most characteristic are the 
following : — 

228. Columbic Anhydride. Cb 2 5 . — A white powder, which 
becomes crystalline when heated, and is afterwards insoluble in 
all acids. It has a Sp. Gr. between 4.37 and 4.53. Before 
ignition, and when in condition of hydrate (Columbic Acid ?), 
it dissolves in strong sulphuric and in hydrofluoric acids. After 
boiling with strong hydrochloric acid, in which it is nearly in- 
soluble, the product dissolves in water, and the solution treated 
with zinc turns blue and finally deposits a blue-colored oxide. 
When a large excess of hydrochloric acid is present, the solu- 
tion deposits a brown oxide under the same conditions ; but the 
constitution of neither of these compounds is as yet known. It 
has been stated that oxides having the composition Cb 2 2 and 
Cb 2 4 have also been obtained. Columbic acid forms salts 
called columbates, and, besides the native compounds mentioned 
above, we are acquainted with several potassic columbates, 
three of which have been obtained in well-defined crystals, but 
they have a very complex constitution. 

229. Columbic Chloride. CbCl 5 . — A yellow crystalline 
solid, melting at 194°, and boiling at 241°. It has been found 



§ 232.] TANTALUM. 297 

by analysis to contain 65.28 per cent of chlorine, and the Qp. 
($>F. of its vapor, by experiment, is 9.6. 

230. Columblc OxycJdoride. CbOCl s . — A white solid, crys- 
tallizing in silky tufts, which volatilizes in the air, without pre- 
viously melting, at 400°. It contains, according to analysis, 
48.9 per cent of chlorine, and the Sp. (@>r. of its vapor has been 
found to be 7.9. Moreover, it has been recently proved that it 
contains oxygen. Both chlorides, when treated with water, 
yield columbic acid. 

231. Columbic Oxyfluoride. CbOF s . — This compound is 
probably formed when columbic acid is dissolved in hydrofluoric 
acid, but it has not yet been isolated in a pure condition. The 
solution, however, forms definite crystalline salts with several 
metallic fluorides, and these are among the most important com- 
pounds of columbium. The salt 2KF . CbOF s . H 2 is very 
readily obtained in nacreous scales, and being far more soluble 
than the compound of tantalum formed under the same condi- 
tions, '2KF . TaF 5 , it gives us the only useful means yet dis- 
covered of separating this element from columbium. A salt 
has also been formed, having the composition 2KF . CbF 5 , and 
isomorphous with the compound of tantalum just mentioned. 
It is interesting as pointing to a fluoride of columbium, CbF 5i 
which is not otherwise known. 

The metal columbium has not with certainty been obtained. 
The black powder described as such by Rose is said to be the 
oxide Cb 2 2 . 

An infusion of gall-nuts gives with acid solutions containing 
columbium a deep orange-red precipitate ; and by this reaction 
columbium may be distinguished from tantalum, which, under 
the same conditions, gives a bright brown precipitate. 

232. TANTALUM. Ta = 182. — This element, associated 
with columbium in the native columbates named above, is the 
chief constituent of Tantalite, Yttrotantalite, and of a few other 
minerals equally rare. Tantalite is i omorphous with colum- 
bite, has the same composition, save only that the acid radical 
is wholly tantalum, and differs chiefly in having a higher Sp. 
Gr., which varies from 7 to 8. Although tantalum is so closely 
allied to columbium, yet its compounds differ from those of this 
last element in several important respects. There appears to 
be no tendency to form oxychlorides or oxyfluorides, — at least 
13* 



298 QUESTIONS AND PROBLEMS. ■ [§232. 

no such compounds are known. The chloride is TaCl 5 , a pale 
yellow solid, melting at 211°, boiling at 242°, and having a 
vapor density = 12.8. It contains by analysis 48.75 of chlo- 
rine, and is decomposed by water, yielding tantalic acid. The 
fluoride, is in like manner, TaF b . It forms double salts with 
the metallic fluoride, the most important of which is the potassic 
fluotantalate, 2KF . TaF 5 , mentioned above. Tantalic anhy- 
dride, Ta 2 5 , is a white powder, insoluble in acids. It closely 
resembles columbic anhydride, and is prepared in a similar way 
from the native tantalates, but it has a higher density (Sp. Gr. 
= 7.6 to 8), and forins with the alkalies a larger number of 
crystalLzed .-alts. There is a hydrate (Tantalic Acid?), and 
also probably several lower oxides of the element. A solution 
of laCl 5 in strong sulphuric acid, when diluted with water and 
reduced with zinc becomes colored blue, but yields no brown 
oxide as in the case of columbium. By reducing sodio-tantalic 
fluoride with sodium, a black powder is obtained which has been 
supposed to be metallic tantalum. 



Questions and Problems. 

1. Calculate the percentage composition of columbite, on the as- 
sumption tint the basic radical is wholly iron and the acid radical 
wholly columbium. Ans. 21.17 FeO and 78.83 Cb,O y 

2. Explain the meaning of the symbol of columbite in (227). 

3. How far do the theoretical £in. Q^v. of columbic chloride and 
oxvchloride compare with the experimental results ? 

4. Th^ mean of twenty analyses of the potassio-eolumbic ovyfluor- 
ide, 2KF. CbOF^ . // 2 0, gave the following results: From 100 parts 
of the salt there were obtained by the process of analysis adopted 
5.87 parts of water, 44.36 of columbic anhydride, 57.82 of potassic 
sulphate, and 31.72 of fluorine. Assuming that the symbol of colum- 
bic anhydride is Cb. 2 O y and estimating the per cent of oxygen by the 
loss, deduce the percentHge composition of the compound and its 
symbol. 

Ans. Columbium, 31.12; Potassium, 25.92; Oxygen, 5.37; Flu- 
orine, 31.72; Water, 5.87. 

5. "What would be the atomic we'ght of columbium if deduced 
from the re-ult of the above analyses ? Ans. 93.9. 

6. Previous to the recent investigations of Marignac, the symbol 



QUESTIONS AND PROBLEMS. 299 



of columbic acid was usually written Cb0 3 when = 8, or Cb. 2 z 
when (J = 16. What prooi's have been given of the correctness of 
the symbol adopted iu tins book ? What was the probable cause of 
the error made by the earlier investigators ? 

7. By what general method may tantalum be separated from co- 
lumbiuiii ? Hoy can you tell when the separation is complete? 

8. What compounds of tantalum and columbium are isomorphous ? 
What bearing does this fact have on the symbol of tantalic anhy- 
dride V Does the vapor density of tantalic chloride agree with the 
symbol which has been adopted ? Why is there a necessary connec- 
tion between the symbol of the chloride and that of the anhydride ? 

9. How may tantalite be distinguished from columbite? 

10. State the resemblances and the differences between the two 
members of tins group of elements. 



CHAPTER XIX. 

THE ARTIAD ELEMENTS. 

Division I. 

233. OXYGEN. 0=16.— Dyad. The most abundant, 
and the most widely diffused of the elements. Forms one fifth 
of the atmosphere, eight ninths of water, more than three fourths 
of organized being-, and one half of* the solid crust of the globe. 

234. Oxygen Gas. 0=0. — Exists in a free state in the at- 
mosphere, but mixed with nitrogen gas. May be extracted 
from the air by either of the following double reactions. Me- 
tallic mercury or baric oxide is first heated in the air, and then 
the products of the first reaction raised to a much higher tem- 
perature. 

1. 2H<j + ®=® = 2HgO. 1. 2BaO + ®-©=2Ba0 2 . r-^-, 

2. 2IJgO=z2Hg-\-©-®. 2. 2Ba0. 2 =2Ba0-\-®=®. L J 

Generally obtained from commercial or natural products, rich 
in oxygen, by one of the reactions given below. The materials 
must in each case be heated to a definite temperature, and the 
last two reactions require a full red heat. 

2KClOz = 2KCI -f 3 (eKD. 1 [229] 

2ICCr 2 7 + \0H 2 SO 4 = 

4{HKSO,) + 2([Cr 2 ]3£0 4 ) -f 877 2 <9-|-3 t>@. [230] 

2Mn0 2 + 2If,S0 4 = 2MnSO i + 2H 2 + ®=®. [231] 

33In 2 = Mn 3 4 -f- ©=©. [232] 

2ff 2 S0 4 = 2H 2 + 2S0 2 + ®=®. [233] 

Also by electrolysis of water and by [66]. Oxygen gas is a 
chief product of vegetable life. Under the influence of the 

1 This reaction is greatly facilitated by mixing the pottissic chlorate with 
cupric oxide or manganic dioxide, which, however, undergo in the process 
no apparent change. 



§235.] OXYGEN. 301 

sun's rays the plants decompose the carbonic acid of their food, 
fixing the carbon and liberating the oxygen. Oxygen gas man- 
ifests intense affinities, but these are only called into play under 
regulated conditions. (Review Chapter XII. on Combustion.) 
When an elementary substance unites with oxygen it is said to 
be oxidized, and when the compound is decomposed the oxide is 
said to be reduced. 

235. Oxygen Compounds. — The most important classes of 
oxides are illustrated by the following symbols and examples: — 

1. R 2 or RR as in H 2 K 2 Ag 2 0, 

2. R,0 2 " h,(R-0)--0 " H 2 2 K 2 2 Ag 2 0» 

3. RO " RO " FeO CaO PbO, 

4. R 2 " (R-R)-O " Cv 2 Hg 2 Pb 2 0, 

5. R0 2 « (R-O)--O " Mn0 2 Ba0 2 Pb0 2 , 
in in in 

6. R 2 3 « (R-OR)W 2 " B 2 3 Au 2 3 Bi 2 3 , 

7. Yl0 2 " R==0 2 " Sn0 2 Si0 2 C0 2y 

IV IV IV 

8. R 2 3 " (R-R)W 3 " Fe 2 3 Al 2 3 Sn 2 3 , 
9. U R 3 \ " R-0 2 =[R 2 y0 2 * Fe 3 A Cr 3 4 Co 3 O i} 

10. R 2 5 « (R-O-R)IO, « N 2 5 P 2 5 As 2 5 , 

11. R 9 A " (R-R)Wt " V 2 A Sb 2 4 Bi 2 4 , 

VI VI 



12. R0 3 " RW 3 " 50 3 /S'eOg MoO { 



As a rule, the oxides of the forms 1 and 3 act as anhydride 
bases (47), and are called protoxides. On the other hand, the 
oxides of the forms G, 7, 10, and 12 generally act as anhydride 
acids. The oxides of the form 8 are called sesquioxide. They 
usually act as basic, but sometimes as acid anhydrides, and at 
other times like the hyperoxides mentioned below. The oxides 
of the forms 9 and 11 are very indifferent bodies, and those of 
the first class are sometimes called saline oxides. The oxides 
of the forms 2 and 5 are called di or hyper-oxides. They act 
as powerful oxidizing agents, readily giving up one half of the 
oxygen they contain [74] [77]. The oxides of the form 4 are 
called suboxides. They sometimes act as anhydride bases, but 
in most cases when acted on by acids they change into protox- 



302 OXYGEN. [§236. 

ides, either giving up one half of the metal or taking up as much 
again oxygen as they contain. The relation of the oxides to 
the acid.-, bases, and salts has been already explained. (Review 
Chapters IX. and X.) 

Besides the above classes of oxides, all of which comprise 
actual compounds, there are others, most of which are only 
known as compound radicals. With many of these radicals the 
student is already familiar, such as S0 2 , SO, N0 2 , NO, PO, in 
all of which the oxygen atoms only satisfy a part of the affini- 
ties of the multivalent atoms, with which they are grouped, and 
the quantivalence of the radical is ea.-ily found by Wurz's rule. 
(28.) The chemists have also been led to assume a very differ- 
ent type of oxygen radicals, in which the affinities of the oxygen 
atoms predominate, and, moreover, it is frequently convenient, 
in expressing the composition of complex compounds, to indicate 
these radicals by a single symbol. The following examples 
illustrate the most important classes of these radicals : — 





Radicals. 


Symbols. 




Examples. 




RO 


(e-6) n 


Ro 


Ho 


Ko 


(Nff 4 )o. 


R0 2 
[f 2 ]0 6 


(O-R-O) 
(OfR-R-O s ) 


Ro 

VI 

R 2 o 


Cao 
AI 2 o 


Zno 
Fe 2 o 


Feo. 
Cr 2 o. 



It will be noticed that the number of oxygen atoms in all 
these cases corresponds to the quantivalence of the metallic ele- 
ment with which they are united, and that the quantivalence of 
the radical is the same as that of its characteristic element. 
Hydroxyl, Bo, is the type of this class of radicals, and names 
may be given to them all formed after the same analogy as 
Potassoxyl, Zincoxyl, — but such names are rarely used. The 
relations of this type of radicals to the three great classes of 
chemical compounds has been already in part illustrated (108), 
and will be still further developed in the present chapter. 

236. Ozone. (0-O) = O.— The best opinion that can at pres- 
ent be formed in regard to the constitution of this remarkable 
substance is expressed by the rational symbol here given. 
Ozone is formed under a great variety of conditions, as, — 1. 
During the passage of electric sparks through air or oxygen. 
2. During the electrolysis of water. 3. During the slow com- 






§236.] OXYGEN. 303 

bustion of phosphorus in moist air. 4. During the slow com- 
bustion of alcohol, ether, and volatile oils. 5. By decomposing 
potassic permanganate with sulphuric acid, and by several other 
similar reactions. Ozone as thus obtained, however, is very 
largely diluted with air or oxygen gas, and we have not yet 
succeeded in preparing it in a pure condition. It differs from 
ordinary oxygen gas, — 1. In having a peculiar odor, with which 
we are familiar, as a concomitant of electrical action. 2. In 
acting as a powerful oxidizing agent at the ordinary temper- 
ature of the air. It corrodes cork, india-rubber, and other or- 
ganic materials. It bleaches indigo. It even oxidizes silver, 
and displaces iodine from its metallic compounds. If a slip of 
paper moistened with starch and potassic iodide is inserted in 
a jar containing the smallest trace of ozone, it is immediately 
colored blue, owing to the liberation of the iodine (119). In 
like manner, paper wet with a solution of manganous sulphate, 
is turned brown by ozone, owing to the oxidaiion of the man- 
ganese, and paper stained with plumbic sulphide is bleached by 
the same agent, because the black sulphide is changed to the 
white sulphate. 3. In the fact that its Sp. Gr. is 24 instead of 
1G. The formation of ozone in a confined mass of oxygen gas 
is attended with a reduction of volume ; and since the ozone thus 
formed may be absorbed by oil of turpentine, we have thus the 
means of determining its specific gravity, and the results, if cor- 
rect, prove that the molecule of ozone consists of three oxygen 
atoms. Again, during most cases of oxidation by ozone, the 
volume of the ozonized oxygen does not change, and this fact is 
consistent with the theory of its constitution which our molecular 
formula expresses, as is illustrated by the following reaction : — 

Ag-Ag + 2(0-0)-0 == Ag 2 2 + 20=0. [234] 

Ti> has been shown, however, that oil of turpentine absorbs 
the molecule of ozone as a whole, and is, therefore, an exception 
to the general rule. The metal in the above reaction is raised 
to the condition of peroxide, and it is probable that several of 
the oxides and oxygen acids contain one or more atoms of oxy- 
gen in the same condition as in ozone. Such compounds have 
been called ozonides, and among them are classed the peroxides 
of silver, lead, and manganese, the sesquioxides of nickel and 



304 OXYGEN. [§237. 

cobalt, as also chromic, manganic, and permanganic acids, with 
their various salts. Ozone appears to be constantly present in 
the atmosphere, and important effects have been attributed to 
its influence. It has been thought to be the active agent in all 
processes of slow combustion and decay, and to play an impor- 
tant part in the economy of nature. At a temperature of 300° 
ozone is instantly changed into common oxygen gas, and at a 
temperature no higher than boiling water, it slowly returns to 

the same condition. 

+ 
237. Antozone. (0-0) = 0. — Whenever ozone is prepared, 

there appears to be tbrmed at the same time a second modifica- 
tion of oxygen gas, which presents such a singular antithesis to 
ozone as to lead us to believe that it is in fact the same sub- 
stance, only oppositely polarized. Hence we have called it an- 
tozone, and assigned to it the symbol at the head of this section, 
although our theory is not based on any conclu-ive experiments, 
and our knowledge of the substance is still very imperfect. It 
may be obtained in several ways, — 1. When dry electrified air 
is parsed through a solution of pyrogallic acid or pota>sic iodide, 
the ozone is absorbed and the air is left charged with antozone. 
2. When baric peroxide is dropped into sulphuric acid, the oxy- 
gen evolved is more or less charged with the same agent. 3. 
When phosphorus is burnt in dry air, a small amount of oxygen 
is always left unconsumed, and this appears to be in the condi- 
tion of antozone. Indeed, it has been supposed that, in all sim- 
ilar processes of oxidation, both ozone and antozone are formed ; 
but that, while the oxygen atoms of the first enter into combi- 
nation with the burning body, those of the last do not, owing to 
their polar condition. 

Antozone has an odor like ozone, but much more repulsive. 
It does not displace iodine or color the iodized paper. It does 
not oxidize silver or the solution of manganous sulphate, but, on 
the contrary, removes from the paper prepared with the man- 
ganous salt the brown stain which ozone had made. On all 
ozonides it acts as a reducing agent. [236.] There is, how- 
ever, another class of substances which it oxidizes, and among 
these the most important is water, with which it forms hydric 
peroxide. 

H 2 0+(0-0) = 6 = B,Bo-'d+ O-O. [235] 



§i37.] QUESTIONS AND PROBLEMS. 305 

In many processes of ozonizing air, the antozone unites with 
and thus condenses the vapor present, although, in most cases 
at least, the union appears to be rather mechanical than chemi- 
cal. The reaction is consequently attended with the formation 
of mists or clouds, which is one of the most striking properties 
of antozone. The smoke of gunpowder, tobacco, and smoulder- 
ing wood has been thought to be an antozone cloud, and the 
clouding of gas jars in many chemical experiments has been 
referred to the same cause. Opposed to the ozonides we have 
a class of antozonides, among which have been classed, besides 
the peroxide of hydrogen, the peroxides of barium, strontium, 
sodium, and potassium, and reactions may be obtained between 
these two classes of compounds which are very interesting. 
They mutually decompose each other, with the evolution of 
oxygen gas, thus : — 

(Pb-O)-O + H,Ho=6 = PbO + IT 2 -f O-O. [236] 

Compare also [75]. Antozone is more unstable than ozone, 
and changes back to oxygen gas at a still less elevation of tem- 
perature. 

Questions and Problems. 

1. What is the reason for writing the symbol of oxygen gas 0=0 ? 
(17) and (19) 

2. What is the difference between the condition of oxygen gas in 
the atmosphere, and that of the same gas in a pure condition con- 
tained in a bell-glass standing over a pneumatic trough? 

3. Were the nitrogen gas of the atmosphere removed, would the 
physical condition of the oxygen gas be changed? 

4. Tf by either of the methods [228] oxygen gas is obtained di- 
rectly from the atmosphere, how many litres of air would be required 
to yield one litre of oxygen gas at same temperature and press- 
ure ? (59.) Ans. 4.77 litres of air. 

5. How much potassic chlorate mu«t be used to yield 100 litres of 
oxygen gis at 30° and 38 c. m. pressure? Ans. 165 grs. 

6. What wei'crht of potassic dichromate [230] must be used to 
yield a litre of oxygen gas, Sp. Gr. = 9G ? Ans. 52.77 grs. 

7. If 32.05 grammes of potassic chlorate are decomposed in a 

T 



306 QUESTIONS AND PROBLEMS. 

closed vacuous vessel of 1,010 c. in. 3 capacity, what will be the tension 
of the gas in the vessel at 273° ? Ans. 131.6 c. m. 

8. What weight of oxygen gas is required to fill a globe of 1 litres' 
capacity at 27°. 3 and 38 c. m. pressure? Ans. 6.515 gram. 

9. From a given weight of Mn0 2 how much more oxygen gas can 
be obtained by reaction [231] than by [232] ? Ans. \ more. 

10. A volume of air measuring 100 c. in. 3 is mixed with 50 c. in. 3 
of hydrogen gas and exploded. What volume of gas is left, as.->um- 
ing that the volumes are all measured under standard conditions, and 
that all the water formed is condensed ? (59.) 

Ans. 87.12 cTnT. 3 . 

11. In an experiment like the last, with the same initial volume 
of air and hydrogen, the volume of the residual gas measured 89.41 
c. m. 3 What is the composition of the air? It is assuim d that the 
volumes are measured under a constant pressure of 76 c. m., and at 
a temperature at which the tension of aqueous vapor equals 2 c. m. 

Ans. 20.96 ox) gen, 79.04 nitrogen. 

12. Analyze reaction [230], and show from which of the factors 
the oxygen is derived. 

13. Represent reaction [232] by graphic symbols. 

14. What volume of chlorine gas is required to decompose one 
litre of aqueous vapor ? Ans. 1 ii re. 

15. If one gramme of water is decomposed by galvanism in a 
closed glass globe containing 1.86 litres of air under normal condi- 
tions, what will be the tension of the resulting gas mixture, leaving 
out of the account the tension of the aqueous vapor which may be 
present? Ans. 152 cm. 

16. Represent by graphic symbols the constitution of the various 
classes of oxides and oxygen radicals. 

17. In the symbols of acids, hydrates, and salts (35) written on 
the water type, to what do the oxygen radicals correspond ? 

18. Explain the change of color which takes ptace when paper 
moistened with a solution of starch and potassic iodide is exposed to 
the action of ozone. 



19. Explain the method of finding the Sp. Gr. of ozone. 

20. Can you devise a method of finding the Sp. Gr. of ozone 
ised on the principle of (58) ? 

21. Explain the reasons for writing the symbol of ozone (0-0)=0. 



QUESTIONS AND PROBLEMS. 307 

22. How would you write the symbols of argentic peroxide and 
plumbic peroxide, on the same principle ? 

23. Why is it essential in preparing antozone that the electrified 
air should be dry ? 

24. In what different ways may the symbol of hydric peroxide be 
written, and what theories of its composition do the symbols suggest? 
By what reactions are these theories sustained ? 



308 SULPHUR. [§238. 



Division II. 

238. SULPHUR. 5=32. — Usually bivalent when in 
combination with metals or positive radicals, but in other asso- 
ciations frequently quadrivalent and sexivalent. Widely and 
abundantly distributed in nature, chiefly in combination, form- 
ing various metallic sulphides and sulphates. The most abun- 
dant of these are iron pyrites, FeS 2 , and gypsum, CaS0 4 . 2H 2 0. 
Found also native in voleanic districts. It is, moreover, an es- 
sential, although a very subordinate, ingredient of the animal 
tissues. Sulphur is very closely allied to oxygen, and, corre- 
sponding to each metallic oxide, there is usually a sulphide of 
the same form ; and, substituting the symbol of sulphur for that 
of oxygen, the table of oxides on page 301 will serve equally 
well as a classification of the sulphides. Moreover, we have 
found it convenient to assume a number of sulphur radicals cor- 
responding in all respects to the oxygen radicals, and we repre- 
sent them by separate symbols formed in a similar way. Thus-, 

I IT II VI 

lis, Pbs, Cw 2 s, Sb 2 s stand for the radicals IIS, PbS 2 , Cu 2 S 2 , 
S^Sa respectively. 

The greater part of the sulphur of commerce comes from the 
mines of Sicily, where it is either melted or distilled from the 
voleanic earth. A small quantity is obtained by roasting or 
distilling iron pyrites. Common sulphur is a very brittle, yel- 
low solid, melting at 114°, and boiling at 440°, when it forms a 
dense red vapor. It is insoluble in water, and nearly so in 
alcohol, ether, and chloroform, but readily soluble in carbonic 
bisulphide, benzole, and oil of turpentine, the solvent power of 
the last two liquids being greatly increased by heat. Sulphur 
assumes a great variety of allotropic modifications, which are 
manifested by differences of crystalline form, specific gravity, 
solubility, and color. At the ordinary temperature it crystal- 
lizes in octahedrons of the orthorhombic system, Sp. Gr. 2.05, 
and above 105° in oblique prisms of the monoclinic systems, Sp. 
Gr. 1.98. Moreover, the one crystalline condition passes into 
the other at the temperature at which it is normally formed. 
If heated to 230°, melted sulphur becomes darker colored, thick, 
and pasty, and if suddenly cooled the mass remains plastic for 



§230.] SULPHUR. 309 

some time. At 100° this plastic material suddenly changes back 
to brittle sulphur, with evolution of heat, and the same change 
soon follows, although more slowly, at the ordinary temperature. 
If sulphur is heated to 230°, and suddenly cooled several times 
in succession, it is in part converted into a peculiar dark-colored 
variety, wholly insoluble in all solvents, and easily separated 
by carbonic sulphide from the unchanged portion. Moreover, 
ordinary flowers of sulphur (formed by condensing the vapor 
of sulphur in cold brick chambers) consist in part of a yellow 
powder, insoluble.in carbonic sulphide, which appears to be still 
another condition of sulphur, and several other modifications, 
including a black and a red variety, have been described as 
di.-tinct allotropic states. Some chemists have thought to find 
among these various modifications a difference of polar condition 
similar to that observed in the modifications of oxygen. Sul- 
phur appears, even in the state of vapor, to present differences 
of condition. Just above its boiling point the Sp. Gr. of sul- 
phur vapor is 96, which corresponds to the molecular formula 
S :i S :i ; and not until the temperature reaches 1,000° does the 
Sp. Gr. become 32, corresponding to the formula *SSS', like that 
of oxygen gas. Sulphur has strong affinities for the metals, 
many of which burn in its vapor with great brilliancy. It has 
also a strong affinity for oxygen. It is \ery combustible, taking 
fire at a low temperature, and forming by burning SO^ It is 
chiefly used for making sulphuric acid, and vulcanizing india- 
rubber ; but it has many subordinate applications both in the 
arts and in medicine. The so-called milk of sulphur, used in 
pharmacy, is obtained by dissolving flowers of sulphur in alka- 
line liquids, and subsequently precipitating with acid. 

239. Hydric Sulphide, Sulphohydric Acid, Sulphuretted 
Hydrogen, N 2 S. — A colorless gas, which by pressure and cold 
may be condensed to a limpid, colorless liquid (Sp. Gr. = 0.9), 
boiling at — 62°, and freezing at — 86°. Is soluble in water 
and alcohol, one measure of water at 0° dissolving 4.37 meas- 
ures, and one volume of alcohol dissolving 17.9 measures, of the 
gas at the same temperature. Has a repulsive odor, and is a 
constant product of decaying animal tissues. Generally obtained 
by the reaction 

FeS + (H 2 S0 4 + Aq) = (FeSO, + Aq) + H 2 S ; [237] 



S10 SULPHUR. [§239. 

but as the ferrous sulphide commonly used contains more or less 
metallic iron, the gas thus prepared is mixed with hydrogen. 
It is obtained in a purer condition from 

Sb 2 S 3 + (%HCl + Aq) = (2SbCl 8 + Aq) + '6H 2 S. [238] 

Hydric sulphide is very combustible, and burns with a pale 
blue flame. 

2ff 2 S + 30=0 = 2ff 2 0-\- 2S0 2 . [239] 

The solution of the gas exposed to the air soon becomes turbid, 
owing to the oxidation of the hydrogen and consequent sepa- 
ration of sulphur. 

(2JT 2 S + Aq) + (fi>® = (2H 2 + Aq) + S=S. [240] 

If the action is assisted by porous solids, the oxidation is more 
complete. 

(H 2 S + Aq) + 2®=® = (fff0 2 *S0 2 + Aq). [241] 

The substance is also decomposed by chlorine, bromine, or 
iodine. 

(2H 2 S+ 2H+ Aq) = (iff! + Aq) + &S. [242] 

On this last reaction is based a simple process of determining 
volumetrically the amount of H 2 S in a given solution. The 
compound may be analyzed by heating metallic tin in a confined 
volume of the gas. 

S3 2 g + Sn — SnS + HHH. [243] 

Although the sulphur is removed by the tin, the volume of the 
gas does not change. Hydric sulphide is not unfrequently 
formed in nature from calcic sulphate, which in contact with 
decaying animal or vegetable matter loses its oxygen, when 
the carbonic acid of the atmosphere, acting on the resulting 
calcic sulphide, sets free the compound in question. It is thus 
that the soluble sulphides in many mineral springs probably 
originate. 

Hydric sulphide is one of the most important chemical re- 
agents, and is used to convert into sulphides various metallic 
hydrates and other salts. 



§239.] SULPHUR. 311 

1. Action on alkaline hydrates. 

(K-0-H+ ff a S+Aq) = (K-S-JI+ H 2 + Aq). [244] 

(K-S-If+ K-0-H+ Aq) = (K 2 S+B 2 + Aq). [245] 

Thus may aLo be formed Na~Hs, JVa^S, NH±Hs, (N1T 4 ) 2 =S. 
(38.) 

2. Action on salts of the more electro-negative metals. 

(CdS0 4 + H 2 S + Aq) = CdS + (H 2 S0 4 + Aq). [246] 
So also may be precipitated from acid solutions of their salts 

As 2 S 3 , Sb 2 S s , Sb 2 S 5 , SnS, SnS 2 , PiS 2 , Av 4 S 4 , 

Yellow. Red. Orange. Brown. Yellow. Brown. Black. 

all of which are soluble in alkaline sulphide?, and 

CdS, CuS, Bi' 2 $ s , A<j 2 S, HgS, [Ea 2 -}S, PbS, 

Yellow. Black. Black. Black. Black. Black. Black. 

all of which are insoluble in alkaline sulphides. 

3. Action on salts of the more electro-positive metals. The 
following sulphides, although not precipitated from acid solu- 
tions, are precipitated when sufficient ammonia is added to neu- 
tralize all the acids present, or when an alkaline sulphide is 
used in place of H 2 S. 

ZnS, MnS, FeS, NiS, CoS. 

White. Pink. Black. Black. Black. 

At the same time aluminum and chromium are also precipitated 
as hydrates. The remaining common metals, viz. : Ba, Sr, Ca, 
Mg, K, and Na. forming sulphides soluble in water, are not pre- 
cipitated by i/^ under any conditions. Thus H 2 S serves to 
divide the metallic radicals into groups, and on these relations 
the ordinary methods of qualitative analysis are based. 

4. Action as reducing agent. 

(lFe 2 ]Cl 6 + ff 2 S+Aq) = 

(2FeCl 2 + 2HCI + Aq) + S. [247] 

(K£ Cr 2 -] 7 + SHCl + SIT 2 S -f Aq) = 

Red - ([<7r 2 ] Ck + 2KCI + 1H 2 + Aq) + S 3 , [248] 

Green. 

10ff 2 S + 10SO 2 = 5S 2 + Sff 2 + 2H 2 S n O Q . [249] 

PentatMoaic Acid. 



312 SULPHUR. • [§240. 

240. Tlydric PersuIpMde, IT 2 S 2 , analogous to IT 2 2 , can be 
obtained by gradually adding to hydrochloric acid sodic bisul- 
phide. It is a yellow, oily liquid, and very unstable. 

241. Alkaline Sulphides and Sulphohydrates. — Solutions of 
the simple sulphides and sulphohydrates are best formed as 
above. These solutions readily dissolve sulphur, and various 
per.-ulphides are thus formed. The following six sulphides of 
potassium are known : K 2 S, K 2 S 2 , K 2 S 3 , K 2 S^ K 2 S 5 , and K 2 S 7 . 
Other modes of preparing similar compounds are illustrated by 
the following reactions: — 

K 2 =0 2 =S0 2 + 4&-H= K 2 S + 4J7 2 <9. [250] 

Ignited in gas current. 

12S+(GK-0-H+Aq) = 

Boiled in solution. {2 K 2 S 5 + K 9 S 2 3 + 31I 2 + Aq). [251] 

Tentasulphide. Hyposulphite. 

1 C,S 4- ZK-0-H= 3K 2 S 5 + K.SOt + 4H 2 0. [252] 

Melted together at a high temperature. 

8S + 3Kf0. f CO = 2K 2 S S + K 2 S 2 3 + 3C0 2 , or k 
US+3Kr Of CO = 2K 2 S 5 + K 2 S a 3 + 3 C0 2 . L 253 ] 

Melted together at a lower temperature. 

The products of the last two reactions are not constant, but 
various persulphides are formed, depending on the temperature 
and the conditions of the process. The resulting mixture is a 
yellow solid called liver of sulphur. When treated wiih acids, 
the various sulphides react as follows : — 

(K-Hs + HCl + Aq) = {KCl + Aq) -f 3H 2 ^. [254] 

(K 2 S + 2HCI + Aq) = (2KCI + Aq) + ISfi. [255] 

(K 2 S 3 + 2HCI + Aq) = {2KCI + Aq) + S 2 + S 2 g. [256] 

{2K 2 S- + K 2 S 2 3 + QIICl + Aq) = 

(QKCl + S0 2 -f H 2 + Aq) + 9S + 2IU 2 ^. [257] 

Solutions of the alkaline sulphides or sulphohydrates absorb 
oxygen from the air, and are thus changed into persulphides 
and hyposulphites. 

(§NH A S-H-\- Aq) + 5©=© = 

Colorless solution. 

(2{NH i ) 2 S 2 +2(NH i ) 2 S 2 3 +W 2 + Aq).[2D$] 

Yellow solution. 



§243.] SULPHUR. 313 

Sulphur and hydric sulphide react on the alkaline earths in 
nearly the same ways as on the alkalies. 

Ca + R 2 S = CaS + R 2 0. [259] 

Ignited in gas current. 

CaSO A + 4H-H= CaS + \H 2 0. [260] 

Ignited in gas current. 

CaSO A +AO=(hS+A CO. [261] 

Ignited together. 

2 CaS + H 2 = 2 =H 2 = Ca-S 2 =R 2 + Ca - OfE, [262] 

Mixed with water. 

(Ca.--0.fH, + 2RS + J?) = 

Passing ** through milk of lime. ^ (^^ + 2 # 2 -f ^). [263] 

By boiling sulphur with milk of lime, a mixture of calcic hy- 
posulphite with various calcic persulphides is obtained, among 
which may be distinguished CaS 2 and CaS 5 . By melting to- 
gether sulphur and calcic hydrate or carbonate, there results a 
mixture of calcic sulphide and calcic sulphate. If pulverized 
charcoal is also added, the product is chiefly calcic sulphide. 

242. Compounds of Sulphur and Oxygen. — The following 
are known : — 



Sulphurous Anhydride 


S0 2 , 


Sulphurous Acid 


Hf0 2 =SO, 


Hyposulphurous Acid 


BrOf(S-0-S), 


Sulphuric Anhydride 


so 3 , 


Sulphuric Acid 


H 2 - 2 = S0 2 , 


Kordhausen Acid 


HfOf(SO a -0'S0 2 ), 


Dilhionic Acid 


II 2 =0 2 =(S0 2 -S0 2 ), 


Trithionic Acid 


Hf0 2 ={S0 2 S-S0 2 \ 


Tetrathionic Acid 


H 2 =0 2 ={S0 2 S-S-S0 2 ), 


Pentathionic Acid 


H 2 =0 2 -(S0 2 -S-S-S-S0 2 ) 



243. Sulphurous Anhydride. S0 2 . — Colorless gas, having 
a familiar suffocating odor. It is easily condensed to a colorless 
liquid, boiling at — 10° and freezing at — 76°; gp. ©r- = 1.49. 
Natural product of volcanic action, and abundantly evolved dur- 
ing the roasting of copper pyrites and other sulphurous ores. 
May be prepared by either of the following reactions : — 
14 



314 SULPHUR. [§244. 

S-S -f 2 ©=® = 2^® 2 . [264] 

Burning. 

2H 2 S0 4 + Bg=z HgS0 4 -{-211,0 + ^® 2 . [265] 
211,80, + C= 2'S@, + @© 2 +2HI 2 (g>. [206] 

s-s + jfii a, = jif/»^ + m© 2 . [267] 

May be decomposed by the reactions 

2£<9 2 + ±HHz= 4// 2 + S-S. [268] 

S0 2 + 3H-H= 2H 2 + JS^Sl [269] 

The first reaction is obtained by passing a mixture of the two 
gases through a red-hot tube ; the second, by adding to the so- 
lution containing S0 2 a small amount of hydrochloric acid with 
a few pieces of zinc. The H 2 S may be detected by a strip of 
paper moistened with a solution of acetate of lead, and the reac- 
tion gives us the means of discovering small quantities of S0 2 . 
Sulphurous anhydride is a powerful reducing agent. Thus 

(2IIIO s + bS0 2 + AR ? + Aq) = 

(/-/+ 5H 2 S0 4 + Aq), [270] 

(As 2 5 + 2S0 2 + 2H 2 + Aq) = 

(As 2 3 + 2H 2 S0 4 + Aq). [271] 

(S0 2 -\-I-I+2IT 2 + Aq) = (R 2 SO i +2m-\-Aq.) [272] 

(2S0 2 + 2H 2 4- Aq) 4- ®=® = (2ff 2 S0 4 + Aq). [273] 

FM> 2 4- ^® 2 = PfoS© 4 . [274] 

It is also a powerful disinfecting and antiseptic agent, and is 
much used for retarding fermentation and putrefaction. It also 
bleaches some of the more fugitive colors, but the effect is fre- 
quently transient, and the reaction not well understood. 

244. Sulphites. — At 0° water absorbs 68.8 times its bulk of 
S0 2 , and three crystalline hydrates have been described, one of 
which has the composition S0 2 . H 2 0, and has been regarded as 
sulphurous acid, but this opinion may be questioned. The aque- 
ous solution acts in all its mechanical relations like the simple 



§246.] SULPHUR. 315 

solution of a gas. Nevertheless, in its chemical relations it acts 
like an acid, and yields, with many of the metallic oxides, hy- 
drates, or carbonates, a numerous class of salts called the sul- 
phites. The following examples will illustrate their general 
composition : - i — 

Uydro-sodic Sulphite H,Na-0 2 =SO . 4H 2 0, 

Disodic Sulphite Na? 2 =SO . 1H 2 0, 

Calcic Sulphite Ca-OfSQ. 

The sulphites are generally best prepared by transmitting a 
stream of S0 2 through water in which the metallic oxide, hy- 
drate, or carbonate is suspended. The alkaline salts are the 
only sulphites which are freely soluble in water. The sulphites 
of barium, strontium, and calcium dissolve to some extent in 
water charged with SO* and in this respect the sulphites re- 
semble the carbonates. Argentic sulphite, which may be read- 
ily obtained by precipitation, undergoes a remarkable reaction 
when boiled with water. 

A 9 fO{SO+(H i O + A q ) = 

Ag-Ag + (IfyOfSO, + Aq). [275] 

245. Hyposulphites. — Hyposulphurous acid has never been 
isolated ; but several hyposulphites may be obtained by passing 
a stream of S0 2 through solutions of the corresponding sul- 
phides, or digesting a solution of the sulphite on powdered 
sulphur. 

S + {NafOfSO + Aq) = (M 2 =0 2 =(S-0-S) + Aq. [276] 

Calcic hyposulphite is formed spontaneously in large quanti- 
ties, both in the refuse lime taken from the purifiers of the gas- 
works, and in the refuse after the lixiviation of the black-ball at 
the alkali works, and from this source sodic hyposulphite is 
now obtained. It is the only hyposulphite of practical value, 
and is not only used in photography, but also for removing the 
last traces of chlorine from the bleached pulp used in paper- 
making, and in the treatment of silver ores. 

246. Sulphuric Anhydride. SO z . — Soft, white, silky-looking 
crystalline solid, melting at 25°, and volatilizing at 35°. May 
be obtained either by distillation from the Nordhausen acid or 



316 SULPHUR. [§247. 

from sodic disulphate, or else by passing a mixture of S0 2 and 
= through a heated tube filled with platinum sponge. 

H 2 =0 2 =(S0 2 -OS0 2 ) = Hf0 2 =S0 2 -f- SOg. [277] 

JVa<f0 2 =(S0 2 -0-S0 2 ) = Na 2 =0 2 =S0 2 -f ^® 3 . [278] 

2&® 2 + ©=© = 2&® 3 . [279] 

It unites with many metallic oxides to form sulphates, and 
baryta burns in its vapor. 

BaO + ^® 3 = Ea©,SO s . [280] 

It has an intense affinity for water, and the heat developed by 
the union is so great that the solid hisses like red-hot iron when 
dropped into the liquid. The product is common sulphuric 
acid. 

247. Sulphurylic Chloride. S0 2 0l 2 .— May be formed by 
the direct union of S0 2 and Cl-Ol under the influence of the 
sunlight, also by the reaction 

H 2 SO± + 2PCl 5 = S0 2 C1 2 + 2PCl,0 + 2HCL [281] 

The product is a liquid boiling at 80° ; Sp. Gr. 1.68. Slowly 
decomposed by water. 

S0. 2 Cl 2 + 2H 2 = RS0 4 + 2HOL [282] 

There have also been described the allied compounds 
H-0-S0 2 Cl and S0 2 T 2 . The relations of these compounds 
to sulphuric acid will be made more evident by writing the 
symbols thus : — 

Bo 2 =S0 2 , Ho,Cl=80 2 , C/. 2 =S0 2 , T 2 =S0 2 . 

248. Sulphuric Acid. H 2 =0 2 =S0 2 or Ho 2 =S0 2 . — The follow- 
ing reactions are interesting as illustrating the constitution of 
this important acid, although of no practical value as methods 
of making it : — 

Ho-IIo -f S0 2 r- Ho 2 =S0 2 , [283] 

ff 2 0+ S0 3 == H 2 0,S0 2 . [284] 

2H 2 -0 2 -SO +0-0= 2H 2 =0 2 -S0 2 . [285] 

S-S + W-0-N0 2 = 2H 2 2 =S0 2 + ANO. [286] 






§248.] SULPHUE. 317 

For the uses of the arts the acid is made in enormous quanti- 
ties by burning sulphur in large brick ovens, and conveying the 
S0 2 ihus formed, together with steam and nitric acid fumes, 
generated simultaneously [135], into large chambers Lned with 
sheet lead. 

1. • S0 2 + 2HN0 3 == H 2 SO± -f 2N0 2 . [287] 

2. 3JS T 2 + H 2 0= 2HN0 3 + NO. [288] 

3. 2NO + 0-0 = 2 N0 2 . [289] 

These reactions may be repeated indefinitely, and it is evi- 
dent that the s-ame quantity of nitric acid would serve to con- 
vert an infinite amount of S0 2 into H 2 SO^ were it not for the 
loss occasioned by the constant draft of air through the cham- 
bers. The reaction consists essentially in a transfer of oxygen 
from the air to the S0 2 , the nitrogen compounds acting as the 
mediator, and the draft yields the requisite supply of oxygen 
gas. When the amount of aqueous vapor is insufficient, there 
forms in the chambers a white crystalline compound of some- 
what uncertain composition, but to which has been assigned the 
symbol (N0 2 ) 2 -(S0 2 -OS0 2 ). When mixed with water, this 
compound breaks up into sulphuric acid and nitrous anhydride, 
so that the formation of the acid may also be represented by the 
following equations, which are thought by some chemists to rep- 
resent the process more accurately than those given above: — 

1. S0 2 + 2HoN0 2 = Ho 2 S0 2 -f 2N0 2 . [290] 

2. AN0 2 + 4S0 2 + 0-0 = 2(N0 2 ) 2 ={S0 2 -OS0 2 ). [291] 

3. {N0 2 ) 2 -{S0 2 -OS0 2 ) + 2H 2 = 

2Ho 2 S0 2 -\- N 2 & . [292] 

4. SN 2 3 + K 2 0= 2HoN0 2 + ANO. [293] 

5. 2NO + 0-0 = 2N0 2 . [294] 

In manufacturing sulphuric acid iron pyrites U now frequently 
used instead of sulphur. This ore, burnt in kilns adapted to 
the purpose, yields a plentiful supply of S0 2 , which is converted 
into sulphuric acid in lead chambers as before. The acid drawn 
from the chambers is very dilute, and for most uses must be 



318 



SULPHUR. 



[§248. 



concentrated by evaporation, which is begun in leaden pans, 
but completed in retorts of glass or platinum. The strongest 
acid thus obtained corresponds to the symbol JI 2 S0 4 . It is an 
oily liquid (oil of vitriol), Sp. Gr. = 1.842, boiling at 327°, and 
crystallizing at a low temperature. If during the evaporation 
the temperature is limited to 205° C, an acid is obtained of the 
composition H 2 SO±. H 2 0, and Sp. Gr. 1.78, which crystallizes 
at 9°, and by limiting the temperature to 100°, still a second 
definite hydrate may be obtained, H 2 SO± . 2H 2 0, which has Sp. 
Gr. = 1.62. Oil of vitriol may be mixed with water in any 
proportion, and the hydration of the acid is accompanied by a 
condensation of volume and a great evolution of heat, the max- 
imum of condensation and the maximum of heat being attained 
when the proportions are such as to form the second hydrate. 
A definite Sp. Gr. corresponds to each degree of dilution, and 
tables have been prepared by which, when the specific gravity 
is known, the strength of the acid may be determined. The 
short table which follows gives all the data required for the 
problems in this book : — 



Per Cent of 


Sp. Gr. 


Per Cent of 


Per Cent of 


Sp Gr. 


Per Cent of 


H 2 SO v 


at 15 J . 


S0 3 . 


H^SOr 


at 15^. 


S0 3 . 


100 


1.8426 


81.63 


50 


1.3980 


40.81 


95 


1.8376 


77.55 


45 


1.3510 


36.73 


90 


1.8220 


73.47 


40 


1.3060 


32.65 


85 


1.7860 


69.38 


35 


1 2640 


28.57 


80 


1.7340 


65.30 


30 


1.2230 


24.49 


75 


1.6750 


61.22 


25 


1.1820 


20.40 


70 


1.6150 


57.14 


20 


1.1440 


16.32 


65 


1.5570 


53 05 


15 


1.1060 


12 24 


60 


1.5010 


48 98 


10 


1.0680 


8.16 


55 


1.4480 


44.89 


5 


1 0820 


4.08 



In consequence chiefly of its strong attraction for water, sul- 
phuric acid disorganizes and blackens both animal and vegeta- 
ble tissues. It is also used as a hygroscopic agent, and, under 
limited conditions, for the dehydration of various chemical com- 
pounds. Its action on different chemical agents has been al- 
ready repeatedly illustrated. (See [04], [231], [26;")].) It 
forms several classes of salts, as is illustrated by the following 
examples : — 



§251.] SELENIUM. — TELLURIUM. 319 

Hydro-sodic Sulphate IIo,yao=S0 2 , 

Disodic Sulphate JSTao 2 =S0 2 and with lOi^O, 

Sodic Disulphate Nao 2 ={S0 2 -0-S0 2 ), 

Cupric Sulphate Cuo=S0 2 . 5If 2 0, 

Ferrous Sulphate Feo-S0 2 . UI 2 O y 

Potassio-ferrous Disulphate Feo={SO=0 2 --SO)=Ko 2 . GIT 2 O f 

Aluminie Sulphate Al^SO^. 18If 2 0, 

Common Alum Ko 2 =(S0 2 )ilAl 2 o . 24^0, 

Zincic Sulphate Zno=S0 2 , 

Dizincic Sulphate Zno^SO, 

Trizincic Sulphate Zno 3 lS. 

The last may be regarded as an orthosulphate, but salts of this 
class are wholly exceptional. 

249. Nordkausen Sulphuric Acid, ITo 2 =(S0 2 -0-S0 2 ), corre- 
sponding to the disulphates in constitution, may be prepared by 
dissolving S0 3 in H 2 S0 A , and has been manufactured tor many 
years at the German town whence it takes its name, by the 
distillation of ferrous sulphate. The manufacture of sulphuric 
acid is one of the most important branches of industry in a civ- 
ilized community, as there is hardly an art or a trade into which, 
in some form or other, it does not enter. 

250. Sulphurous Chloride. S 2 Cl 2 . — Yellow, volatile, fuming 
liquid, formed by distilling sulphur in an atmosphere of chlorine 
gas. It is a powerful sulphur solvent, ami has been used for 
vulcanizing india-rubber. It is decomposed by water, but mixes 
with benzole and carbonic sulphide. Sulphuric chloride, SCl^, 
and several oxvchlorides of sulphur are also known. 

251. SELENIUM. Se = 79.4. TELLURIUM. Te = 
12S. — Two very rare elements, clo=ely allied to sulphur, but 
presenting such differences as might be anticipated in elements 
of the same chemical series. They form compounds with hy- 
drogen, H 2 Se and H 2 Te, analogous to U 2 S, and compounds with 
oxygen and hydrogen resembling sulphurous and sulphuric acids. 

Selenium, which follows in the series next to sulphur, mani- 
fests its relationship in many ways. The elementary substance, 
•which in its ordinary condition is a brittle solid having a glassy 
fracture and a dark brown color, Sp. Gr. 4.3, may be obtained 
in several allotropic states, and in one of these, when its Sp. Gr. 



320 SELENIUM. — TELLURIUM. [§251. 

= 4.8, it has the same mono-clinic form and molecular volume 1 
as the corresponding condition of sulphur. It readily melts at 
a varying temperature above 100°, depending on its condition, 
and at 700° is converted into a deep yellow vapor which has 
been observed to have, at a high temperature, Sp. Gr. = 82. It 
burns in the air with a blue flame, forming chiefly Se0 2 , and 
emits an offensive odor resembling putrid horseradish. Hydric 
selenide, also, is a gas with a disgusting smell, which, like H 2 S, 
precipitates many of the metals from solutions of their salts as 
selenidcs. Selenic acid is a thick oily liquid like sulphuric acid, 
and many of the selenates cannot be distinguished by merely 
external characters from the corresponding sulphates. Sele- 
nium, moreover, is almost invariably found in nature associated 
with sulphur, and is extracted from the residues resulting from 
the treatment of sulphur ores. There are, however, a few rare 
minerals which consist mainly of metallic selenides. Among 
the most important of these may be named Clau.-thalite, PbSe, 
Berzelianite, CuSe, Naumannite, Ag 2 Se, and Onofrite, HgSe. 

When we descend in the series to Tellurium, we find more 
marked differences. The elementary substance has a silver- 
white color, a bright metallic lustre, and outwardly resembles a 
metal. It is closely allied in many of its physical properties to 
bismuth. It crystallizes in rhombohedrons, and the mineral 
Tetradymite has been regarded as an isomorphous mixture of 
native tellurium with native bismuth. Its Sp. Gr. = G.2, and 
its atomic volume is very much nearer that of bismuth and an- 
timony, than that of selenium and sulphur. Nevertheless, in 
other relations it is closely allied to selenium. It is hard and 
brittle, a poor conductor of heat and electricity. It fuses be- 
tween 425° and 475°, and at a high temperature yields a yellow 
vapor which has a specific gravity corresponding to the molec- 
ular formula Te = Te. When heated in the air, it burns with a 
greenish blue flame, and is converted into tellurous anhydride, 
Te0 2 . Lastly, hydric telluride resembles closely hydric sele- 
nide, and the sals of tellurous and telluric acids are similar to the 
corresponding selenites and selenates ; but telluric acid does not, 
like selenic acid, form salts corresponding to the alums, and its 

1 The quotients obtained by dividing the molecular weights of different 
solid substances by thrir respective specific gravities may be regarded as 
proportional to their molecular volumes in the solid state. 



§ 252.] MOLYBDENUM. 321 

salts are less stable. Tellurium is the chief constituent of a few 
native compounds which are highly prized as minerals. Be- 
sides Tetradymite, Bi 2 Te 3 , we have Hessite, Ag 2 Te, Sylvanite, 
AgAuTe^ Altaite, Pb r fe, and Nagyagite, which is a sulphotel- 
luride of lead and gold of somewhat uncertain composition. 
The elements of this group form then, evidently, a very well- 
marked series, in which, as in the chlorine series, the chemical 
energy diminishes as the atomic weight increases. 



Division III. 

252. MOLYBDENUM. Jfo = 96. One of the rarer ele- 
ments, but not unfrequently met with in the mineral kingdom, 
usually in combination with sulphur forming the mineral Molyb- 
denite, MoS 2 . which so closely resembles foliated graphite that 
the two might easily be mistaken for each other. From this 
mineral we readily obtain by roasting, at a low red heat in a 
current of air, molybdic anhydride, MoO s , which is the most 
characteristic compound of the element. When pure, the an- 
hydride is a pale buff-colored powder, fusing to a straw-colored 
glass at a red heat, and volatilizing at a higher temperature. It 
is only sparingly soluble in water, but readily dissolves in ordi- 
nary acids, in aqua ammonia, and in solutions of the alkaline 
hydrates or carbonates, and forms with metallic oxides a nu- 
merous class of salts called molybdates. Plumbic molybdate 
(Wulfenite), Pb=0 2 =Mo0 2 , is sometimes found in beautiful yel- 
low or red crystals associated with other lead ores, and molyb- 
date of ammonia, (NH A ) 2 =0<fMo0 2 , is much used in the labor- 
atory as a test for phosphoric acid. Besides MoO s , the 
element also forms compounds with one and with two atoms 
of oxygen, MoO and Mo0 2 , which act as basic anhydrides, 
and there is also an intermediate oxide having a beautiful 
blue color, and another having a dull green color, which are 
formed by the action of SnCl 2 and other reducing agents on 
acid solutions of the molybdates, and the accompanying change 
of color serves as a very striking test for molybdenum. In so- 
lutions of molybdic acid or of molybdates, when acidified with' 
hydrochloric acid, H 2 S, gives a browni«h-black precipitate of 
MoS 3 , and there is still a third sulphide, MoS 4 , which, as well 
14* u 



322 TUNGSTEN. [§253. 

as the last, acts as a sulphur acid. There are also two chlorides, 
MoCl 2 and MoCl 4 . The elementary substance is a brittle silver- 
white metal (Sp. Gr. = 8.6), which is unalterable in the air and 
very infusible. It can be obtained without difficulty by redu- 
cing the oxides with charcoal or hydrogen, but unless the tem- 
perature is very high the metal is left as a gray powder. The 
name is from the Greek, and signifies ''a mass of lead." 

253. TUNGSTEN. W= 184. — This element occurs in 
tolerably large quantities combined with calcium in the mineral 
Scheelite, Ga W0 4 , and with both iron and manganese in Wol- 
fram, of which there are two varieties, 2Fe W0 4 -\- 3Mn WG 4 
and \Fe W0 4 -\- Mn W0 4 . Both minerals are decomposed by 
acids, and by this means we readily obtain tungstic anhydride, 

W0 3 , a yellow powder insoluble in water and acids, but readily 
dissolving in ammonia and solutions of alkaline hydrates, and 
even decomposing with effervescence the alkaline carbonates, 
when heated in solutions of their salts. From a boiling alkaline 
solution of tungstic anhydride the common acids throw down a 
yellow precipitate of tungstic acid, H 2 WO A . This acid forms 
with bases a numerous class of salts called tungstates, which, 
although of litfle practical importance, are theoretically very 
interesting, and have been the object of careful investigation. 
There are several (at least two) distinct types of these salts, 
and there are also two modifications of tungstic acid ; for, be- 
sides the ordinary insoluble condition, both molybdic and tung- 
stic acids have been obtained in a colloidal condition, in which 
they are very soluble in water (57). The tungstates have the 
same crystalline form as the corresponding molybdates, and a 
tungstate of lead, isomorphous with Wulfenite, is a well-known 
mineral called Scheeltine. Besides WO s there is an oxide, W0 2 , 
which also acts as an acid anhydride, and there is also an inter- 
mediate oxide of a splendid blue color, which may be produced 
by the action of reducing agents on the anhydride or the soluble 
tungstates. Tungsten is not, like molybdenum, precipitated by 
H 2 S, but the sulphide, WS 2 , has been prepared artificially, and 
resembles very closely the native molybdenite. There is also 
a sulphide, WS 3 , and there are two volatile chlorides, WGI 4 and 

WG! 6 . The metal itself (Sp. Gr. 17.6) is easily reduced, but, 
in consequence of its great infusibility, cannot be obtained in a 
compact state except at a very high temperature. It has an 



§253.] QUESTIONS AND PROBLEMS. 323 

iron-sray color, and, when alloyed with steel to the extent of 8 
or 10 per cent, renders the metal exceedingly hard. The com- 
pounds neither of tungsten nor of molybdenum have found any 
important applications in the arts, although sodic tungstate has 
been used, mixed with starch, in finishing cambrics, because it 
has been found to render these light fabrics less inflammable. 
The name tungsten had a Swedish origin, and signified in the 
original '* heavy stone." 

Questions and Problems. 

1. What is the per cent of sulphur in gypsum and iron pyrites? 

Ans. 53.33 per cent and 18.6 per cent. 

2. Write the symbols of the different classes of sulphides. 

3. Express by graphic symbols the constitution of the various sul- 
phur radicals. 

4. What are the atomic volumes of the two crystalline varieties of 
sulphur? Ans. 15.60 and 16.16. 

5. By heating 10.000 grammes of silver in the vapor of sulphur, 
Dumas obtained 1 1.4815 grammes of argentic sulphide. What is the 
atomic weight of sulphur ? What assumption is made in your calcu- 
lation, and what ground have you for this assumption ? 

Ans. 32.000. 

6. What is the specific gravity of H 2 S gas referred to hydrogen 
and to air? Ans. 17 and 1.1764. 

7. What weight of sulphur is contained in one litre of H 2 S? 

Ans. 1.434 grammes. 

8. How much antimonious sulphide is required for the preparation 
of one litre of hydric sulphide ? How much to prepare 340 grammes ? 

Ans. 5.076 grammes, 1133.33 grammes. 

9. What volume of oxygen gas is required to burn one litre of 
H 2 S, and what are the volumes of the aeriform products? 

Ans. l\ litres of oxygen gas, one litre of aqueous vapor, and one 
of sulphurous anhydride. 

10. One litre of (H 2 S -}- Aq) saturated at 0° will absorb what 
volume of oxygen gas, and will yield what weight of sulphur? 

Ans. 2.185 litres, 6.263 grammes. 

11. Assuming that a solution of iodine in a solution of potassic 
iodide has been prepared of known strength, how may this be used 
to measure the quantity of H 2 S in a mineral water ? 



324 QUESTIONS AND PROBLEMS. 

12. The specific gravity of hydric sulphide has been found by ex- 
periment to be 17.2, and by reaction [243] it is shown that one vol- 
ume of the gas contains an equal volume of hydrogen. Show that 
these results agree quite closely with the molecular symbol assigned 
to the compound. How do you explain the slight discrepancy ?. 

13. Write the reactions by "which hydric sulphide is formed from 
calcic sulphate. 

14. Write the reaction by which NH^Hs may be formed from 
aqua ammonia. 

15. Write the reaction of ff 2 S gas on solution of plumbic acetate, 
and calculate what volume of (ll 2 S -\- Aq) saturated at 0° would be 
required to precipitate 0.207 grammes of lead. 

Ans. 5.109 cTHT. 3 of H 2 S + Aq. 

16. Write the reaction of H 2 S on solution of acetate of zinc. 
What inference would you draw from the fact that Zn is precipitated 
by this reagent from an acetic acid solution, while Fe and Mn are 
not ? 

17. Into what groups may the metallic radicals be divided by 
means of the two reagents hydric sulphide and ammonic sulphide, 
and how must the reagents be used in order to separate these groups 
from a given solution ? 

18. In reducing 28 grammes of iron from the condition of ferric 
to that of ferrous chloride, how much sulphur is precipitated ? 

Ans. 8 grammes. 

19. Analyze the reactions [248] and [249], and show how the 
HiS gas acts as a reducing agent in each case. 

20. Write the reaction of hydrochloric acid on sodic bisulphide. 

21. Represent by graphic symbols the constitution of the various 
potassic sulphides. 

22. Analyze reactions [250] to [263]. 

23. Write reaction when sulphur and milk of lime are boiled to- 
gether, assuming, first, that CaS 2 , and second, that CaS 6 , is produced. 

24. Write reaction when sulphur and calcic hydrate are melted 
together, assuming that CaS & and CaSO i are produced. 

25. Represent by graphic symbols the composition of the com- 
pounds of sulphur and oxygen. 

26. Is the quantivalence of sulphur in the sulphites and hyposul- 
phites the same as in the sulphates, &c. ? 



QUESTIONS AND PROBLEMS. 325 

27. What volume of sulphurous anhydride would be formed by 
burning 2.8672 grammes of sulphur? Ans. 2 litres. 

28. It has been observed that when sulphur burns in oxygen the 
volume of the product is the same as the initial volume of oxygen 
gas. It has been found by experiment that the Sp. Gr. of sulphur- 
ous anhydride equals 32.25. How do these facts correspond with the 
molecular symbol usually assigned to the compound ? What is the 
Sp (&>X- of S0 2 referred to air? Ans. 2.234. 

29. How much mercury is required to make one litre of &0 2 ? 

Ans. 8.9G grammes. 

30. Leaving out of view the value of the mercury used, as it may 
be easily recovered, by which of the two reactions [265] or [266] 
may S0 2 be most profitably prepared ? 

3 1 . How much Mn 2 would be required to yield by reaction [26 7] 
sufficient SO a to neutralize 1.29 grammes of sodic carbonate? 

Ans. 1.059 grammes. 

32. Point out the volumetric relations in reaction [268]. 

33. Are the conditions under which the reaction [269] is obtained 
in any way peculiar ? 

34. Compare reactions [271] and [272], and inquire whether a 
method of volumetric analysis based upon them might not be devised. 

35. Represent by graphic symbols the sulphites whose symbols are 
given in (244). 

36. The refuse lime of the gas and alkali works contains calcic 
disulphide, CaS 2 . In what way would this be changed by exposure 
to the air into calcic hyposulphite, and how from this product could 
sodic hyposulphite be prepared ? 

37. Write the reaction of hydrochloric acid on sodic hyposulphite, 
knowing that hyposulphurous acid, when liberated, breaks up into 
sulphurous anhydride and sulphur. 

38. The specific gravity of the vapor of sulphuric anhydride has 
been found by experiment to be 39.9. How does this agree, with the 
theoretical value? Compare the densities of 0=0, S0 2 , and S0 S as 
regards the relative degree of condensation in each. 

39. What are the relations of the compounds S0 2 CI V S0 2 ClHO, 
S0 3 , and H 2 SO i to each other? 

40. Analyze the two sets of reactions [287 et seq."] and [290 et ^7.], 
and show from whence the oxygen required to oxidize the sulphur- 
ous acid is derived, and what part the oxides of nitrogen play in the 
process. 



326 QUESTIONS AND PROBLEMS. 

41. In the process of making oxygen gas from sulphuric acid, from 
whence is the oxygen in the first instance derived ? Might not 
the same quantity of acid be made to yield an indefinite supply 
of gas ? 

42. It appears by experiment that the Sp. Gr. of H^SO^ vapor is 
24.42. How does this agree with theory, and how do you explain 
the discrepancy ? 

43. It has been found by exact experiments that 100 parts of lead 
yield 146.45 parts of plumbic sulphate. What is the molecular 
weight of su'phuric acid ? What assumption does your calculation 
involve (68) ? Why do you regard this result as more trustworthy 
than that of the last problem ? Ans. 98.16. 

44. How do the symbols of the hydrates of sulphuric acid compare 
with those of the crystalline salts of this acid ? 

45. AVrite the symbols of sulphuric acid and its two hydrates, rep- 
resenting them as compounds of S0 2 with hydroxyl. Point out the 
distinction between the ortho and meta acids, and show that a simi- 
lar distinction may be made among the salts. 

46. How many litres of sulphuric acid, Sp. Gr. = 1 615, can be 
made from 1,000 kilos, of pyrites, assuming that all the sulphur in the 
mineral is burnt ? Ans. 1444.4 litres. 

47. How much sulphuric acid by weight, Sp. Gr. = 1.501, will be 
required, 1st. To neutralize 53 grammes of sodic carbonate? 2d. To 
dissolve 32.6 grammes of zinc ? 3d. To precipitate completely 2.08 
grammes of baric chloride? 

Ans. 81.666 grammes, 81.666 grammes, 1.633 grammes. 

48. Represent the constitution of the various sulphates by graphic 
symbols. 

49. In what does the symbol of dizincic sulphate differ from that 
of a sulphite? 

50. If the specific gravity and molecular weight of a solid sub- 
stance be given, how can you find the molecular volume of the 
substance in the solid condition ? 

51. How does the molecular volume of sulphur compare with that 
of selenium, 1st. In the solid condition ? 2d. In the crystalline con- 
dition ? 

52. What is true of the molecular volumes of all substances in the 
state of gas ? 

53. Compare the molecular volumes of tellurium and bismuth. 



QUESTIONS AND PROBLEMS. 327 

54. What are the analogies, and what are the chief points of dif- 
ference between sulphur, selenium, and tellurium ? 

55. Write the reaction of hydric selenide on a solution of plumbic 
acetate, also of potassic selenate on a solution of baric chloride ? 

56. Write the reaction when Molybdenite is roasted in the air. 

57. Write the reaction of H 2 S on a solution of molybdic acid in 
hydrochloric acid. 

58. What is the relative proportion of tungstic anhydride in the 
two varieties of Wolfram? Ans. 76.47 to 76.38 %. 

59. Write the reaction of hydrochloric acid on Scheelite. 

60. In what respects does tungsten resemble molybdenum? 

61. What is the atomicity of tungsten and molybdenum, and what 
is the prevailing quantivalence in each case ? 



328 COPPER. [§254. 



Division IV. 

254. COPPER. Gu = 63.5. — Dyad. One of the most 
abundant metals, and known from great antiquity. Of its ores, 
by far the most important is Copper Pyrites, Fe=S 2 =Cu, which 
is found to a greater or less extent in almost all countries. 
This mineral resembles iron pyrites, but is distinguished from 
it by greater so r tness and a ruddier tint. The smelting of the 
ore is a complex process, and consists in an alternating series 
of roastings and meltings, during which the iron passes into the 
slags, while the copper accumulates in the successive "mattes," 
as they are called, until at last a nearly pure sub-sulphide is 
obtained. This is now heated in a current of air until the metal 
is partially oxidized, and then the mass is melted, when the 
following reaction results : — 

2CuO+ Cu 2 S = 4 Ca -f S0 2 . [295] 

The crude metal thus obtained must, however, be subsequently 
refined. To this end it is first kept melted in the air for many 
hours, until all the impurities are oxidized; and then the oxides 
of copper, formed at the same time, are reduced by submitting 
the mass to the action of carbonaceous gases, which are gener- 
ated by thrusting a stick of green wood under the molten metal. 

255. Metallic Copper. Cu. — Found native crystallized in 
forms of the isometric system. Has a brilliant lustre, and a 
familiar reddish color. Has great hardness and tenacity. Is 
very ductile and malleable, and one of the best conductors of 
heat and electricity. Sp. Gr. 8.8. Fuses at about 780°. Vol-r 
atilizes only at a very high temperature. Its vapor burns with 
a beautiful green flame, which shows in the spectroscope char- 
acteristic bands. Under ordinary conditions copper undergoes 
no change in the atmosphere, but if heated to redness in the air 
it is rapidly oxidized. In presence of acids or solutions of chlo- 
rides, like sea-water, copper absorbs oxygen from the air at the 
ordinary temperature, and is more or less rapidly corroded. A 
similar effect is also produced by aqua ammonia and solutions 
of ammonia salts. Out of contact with the air, dilute hydro- 
chloric or sulphuric acids have but little action upon metallic 



§ 257.] COPPER. 329 

copper. If boiled with strong hydrochloric acid, it very slowly 
dissolves with the evolution of hydrogen gas. Under the same 
conditions sulphuric acid, if not too dilute, is decomposed by it, 
cupric sulphate is formed, sulphurous acid is evolved, and the 
reaction is similar to [265]. Nitric acid is the best solvent, 
but, singularly, the strongest acid has no action on the metal. 
"When diluted with water, however, the action is very violent; 
cupric nitrate is formed, and a gas is evolved which is generally 
NO ; but when the acid is very dilute this product is more or 
less mixed with N 2 0. 

256. Cupric Oxides. [ Cu 2 ~] and Oa 0. — Both of which act 
as basic anhydrides, although the salts of the second are by far 
the most stable and important compounds. [Cu 2 ~\0 has a red 
color, and when melted into glass imparts to it a beautiful ruby 
or purple color. It is the Red Oxide of Copper of mineralogy, 
and is found massive and beautifully crystallized in various 
forms of the isometric system, also in splendid capillary tufts 
(Chalcotrichite). CuO is black, but imparts to glass a green 
color. It is found sparingly in nature, rarely crystallized 
(Black Oxide of Copper, or Melaconite). May be prepared by 
roasting copper or igniting the nitrate. Is very ea>ily reduced 
by hydrogen [67] or carbonaceous materials, and is much used 
as an oxidizing agent in the process of organic analysis. The 
following reactions illustrate some of the relations of these 
oxides and their hydrates: — 

When cold, (Cu=0 2 =S0 2 + 2K-0-JT+ Aq) = 

Cll0 2 H 2 + (KfOfS0 2 +Aq). [296] 

Byboiling, (Cu = 2 =ff 2 +Aq)=CnO+(ff 2 0+Aq). [297] 

Blue. Black. 

By boiling with grape sugar, 

(2Cu=0 2 =S0 2 + iK-O-H— 0+A g ) = 

[Cu 2 ]0 + (2K 2 =0 2 =S0 2 + 2H 2 + Aq). [298] 

Red. 

An orange-yellow hydrate, 4[Cu 2 ~\0 . H 2 0, is precipitated on 
first warming the liquid, but this is rendered anhydrous by 
boiling. 

257. Cupric Sulphate (Blue Vitriol). Cu=0 2 =S0 2 . bH 2 0.— 
The most important soluble salt of copper. Although when pure 



330 copper. [§258. 

it always crystallizes with five molecules of water, as above, yet 
it is capable of forming isomorphous mixtures with ferrous sul- 
/ phate, Fe = 2 = S0 2 . 7 H 2 0. When in this mixture the copper is 
in excess, the crystals take bH 2 and the form of cupric sul- 
phate (Fig. 28). If, however, the iron is in excess, they take 
1H 2 and the form of ferrous sulphate, similar to Fig. 26. The 
anhydrous salt is white, but becomes blue on uniting with water, 
for which it has a very strong affinity. Of the five molecules 
of water with which the crystalline salt is united, one is held 
much more firmly than the other four, and may be replaced by 
a molecule of an alkaline sulphate. This gives a reason for 
writing the symbol of the salt thus, Ho 2 ,Cuo=SO . AH 2 0. In 
like manner the symbols of several so-called basic salts may be 
written thus, 

Ho,{Cu0 2 H)^SO, 

Ho 2 \ Cu 2 H ) 4 iS (Brochantite), 

Ho,(Cu0 2 H) 5 iS.2H 2 0, 

in which the group Cu0 2 II acts as a monad radical. From 
solutions of cupric sulphate the copper is readily precipitated 
by Zn or Fe. 

Zn + (CuS"0 4 + Aq) = Clt + (ZnS0 4 -f Aq). [299] 

258. Carbonates. — Malachite, (Cu0 2 H) 2 = CO. Same com- 
pound may be obtained by mixing hot solutions of cupric sul- 
phate and sodic carbonate. Azurite, Cuo 3 ,flo 2 vm C 2 or 
Uo,Cuo = C-Cuo-C a Cuo,Ho. Mysorin, Cuo 2 ^C. The normal 
carbonate is not known. 

259. Nitrates. — Cuo = (N0 2 ) 2 . 6J7 2 when crystallized be- 
low 60°, and Cuo = {N0 2 ) 2 . 2>H 2 when crystallized above 00°, 
a deliquescent blue salt. A green basic nitrate has the symbol 
Ho.,. ( Cu 2 H)^ Cuo ™\N 2 0. 

260. Cupric Phosphate, Cuo z \{PO) 2 , is obtained on adding 
a solution of sodic phosphate to a solution of cupric sulphate. 

261. Cupric Silicate. Dioptase, Ho,{ Cu0 2 H)=SiO. 

262. Sulphides : — 

Copper Glance \_Cn 2 ~\S, 

Covelline (Indigo Copper) CuS, 

Copper Pyrites Fe=S 2 =Cu, 

Erubescite Fe =S 2 =([ Cu 2 ~\ -S-[ CkJ), 

Tetrahedrite [Cu 2 y=S^Sb 2 . ZnS. 



§2G7.] COPPER. 331 

When H 2 S is passed through the solution of a copper salt, a 
black precipitate falls having the composition Cu & S b Ho 2 , which 
rapidly oxidizes in the air. 

263. Fluohydrate of Copper. (CuOH)-FL 
Chlorides. — Cuprous Chloride, [Cw 2 ] Cl 2 . White compound, 
insoluble in water, crystallizes in tetrahedrons. Cupric Chloride, 
CuCl 2 . 2H 2 0, crystallizes in green needles, very soluble in both 
water and alcohol. Cupric Oxichloride, ( Cu 4 3 yCl 2 . 4ff 2 0, is 
much u.-<ed as a paint (Brunswick green), and the mineral Atac- 
amite is the same compound, with only one, or at most two, mole- 
cules of H 2 0. 

2G4. Cupric Hydride. CuH 2 . — A brown powder, which gives, 
with hydrochloric acid, the following remarkable reaction : — 

CuH 2 + (2HCI + Aq) = ( Cu Cl 2 + Aq) -f 2II-K [300] 

2G5. Ammoniated Compounds. — When a solution of ammo- 
nia or of ammonia carbonate is added to a solution of a salt of 
copper, the light-green precipitate first produced readily dis- 
solves in an excess of the reagent, producing a deep-blue solu- 
tion ; and this striking coloration is one of the most characteristic 
tests of the presence of copper. The effects are caused by the 
formation of certain remarkable compounds, in which a portion 
of the hydrogen of the ammonia appears to have been replaced 
by copper. The following are a few examples: — 

(H 2 .H 2 # 2 IiV>[ Cu 2 -\)- C! 2 , (H»H 2 ;{NH A )^Nti tf/ 2 ])=4 
{H 2 ,H 2 Mf-N 2 -Cu)-C\ {H^H^NH^N^Cuy-SO, . H 2 0. 

266. Characteristic Reactions. — The presence of copper in 
a solution may be readily detected, not only by ammonia as in- 
dicated above, but also by the action of polished iron (a needle, 
for example), which, in a feebly acid solution, soon becomes 
covered with a red metallic coating. Copper ores, when mixed 
with fluxes, are readily reduced on charcoal before the blow- 
pipe, and this is one of the best means of recognizing such 
compounds. 

267. Uses. — Besides the numerous uses of the metal itself, 
copper is employed in the arts still more extensively when 
alloyed with other metals. The varieties of brass and yellow 
metal are alloys of copper and zinc in different proportions, 



332 MERCURY. [§ 268. 

while bronze, bell-metal, gun-metal, and speculum-metal are all 
essentially alloys of copper and tin. Several of the compounds 
of copper are much used as paints. 

268. MERCURY. Hg = 200. — Dyad. This element is 
not widely disseminated, but its ores are abundant in a few lo- 
calities, of which the most noted are Idria in Austria, Almaden 
in Spain, New Almaden in California, and Huancavelica in Peru. 
The ores at all these localities consist chiefly of Cinnabar, HgS y 
but they frequently contain a small quantity of the metal in the 
native state. They are easily smelted, the sulphur of the ore 
serving as fuel. The assorted ores are arranged in layers in 
kilns of peculiar construction, and the mass kindled with brush- 
wood. As the sulphur burns away, the mercury is volatilized, 
and the products thus formed are passed through earthen pipes 
("aludels") or brick chambers, which condense the mercury 
vapor, while the S0 2 gas escapes into the atmosphere. 

HgS+ 0-0 = Hg -f S0 2 . [301] 

In the Palatinate, mercury is obtained from cinnabar by mixing 
the ore with slaked lime and distilling in iron retorts. 

AHgS + 4 Ca = 3 CaS + CaS0 4 + Hg. [302] 

269. Metallic Mercury. Hg. — The only metal liqu : d at or- 
dinary temperatures. Freezes at — 40°. Boils at 350° and 
evaporates, but only with exceeding slowness at the ordinary 
temperature. Sp. Gr. of liquid, 13.596. Sp. Gr. of vapor by 
experiment, 100.7. Has a brilliant metallic lustre, silver-white 
color. In solid condition is malleable, crystallizes in octahedrons, 
Sp. Gr. 14.4. In contact with the air pure mercury undergoes 
no change at the ordinary temperature, but if boiled in the at- 
mosphere, it is slowly converted into HgO. Hydrochloric acid 
is without action on the metal, and the same is true of dilute 
sulphuric ncid. Strong sulphuric acid, however, is decomposed 
by it [265]. The best solvent is nitric acid, which yields dif- 
ferent products according to the proportions of metal, acid, and 
water used. Chlorine, Bromine, Iodine, and Sulphur all enter 
into direct union with mercury. By simple trituration the liquid 
metal admits of being mechanically mixed in a state of minute 
subdivision with chalk and with saccharine or oleaginous sub- 



§272.] MERCURY. - 333 

stances, and many important pharmaceutical preparations are 
made in this way, — blue-pills, mercurial ointments, etc. 

270. Oxides of Mercury. — Mercurous Oxide, \_Hy 2 ~\0. 
Black powder, very unstable. Decomposed by exposure to light 
or to a very gentle heat. \Hg>i\ ==■ HyO -\- Hg. Mercuric 
oxide, HyO. Red crystalline scales or yellow powder, according 
to mode of preparation. Stable compound, but decomposed at 
red heat into mercury and oxygen [228]. No corresponding 
hydrates are known, but both oxides form stable salts. 

271. Nitrates. — Mercurous nitrate is obtained by dissolving 
metallic mercury in an excess of nitric acid diluted with four or 
five times its bulk of water. Mercuric nitrate is best obtained 
by dissolving mercuric oxide in an excess of nitric acid. These, 
like other salts of mercury, tend to form basic compounds. 

Mercurous Nitrate \_Hg 2 ~\ = 2 =N 2 0±.2H 2 0, 

Dimercurous Nitrate (\_Hg 2 ~]~0 -\_Hy 2 ~\y0 2 =N 2 0^ 
Trimercurous Di nitrate 

([^ 2 ]-0-[^ 2 ]-0-[^ /2 ])=0 2 =(^ 2 4 -0-^ 2 4 ) . 3H 2 0, 

Mercuric Nitrate By = 2 =JV 2 4 . 2H 2 (9, 

Dimercuric Nitrate (Hy-OHyy0 2 -N 2 4 . 2H 2 0, 

Trimercuric Nitrate (Hy-0-Hy-0-Hy) = 2 =JSr 2 4 . H 2 0. 

A solution of mercurous nitrate with caustic soda gives a 
black precipitate of mercurous oxide. 

(l^l-O^O, + 2M-0-H+ Aq) = 

[JfyJ + (2Na-0-N0 2 + H 2 + Aq). [303] 

A solution of mercuric nitrate with caustic soda gives a yel- 
low precipitate of mercuric oxide. 

(Hg = 0. r N 2 4 + 2Na-0-HJ r Aq) ~= 

HyO + (2Na-0-N0 2 + H 2 + Aq). [304] 

Mercurous nitrate, if heated, is converted into the red crys- 
talline variety of mercuric oxide. 

[Hy 2 -]= 2 -N 2 4 = 2Hy0 + 2N0 2 . [305] 

272. Sulphates. — When mercury is gently heated with an ex- 
cess of strong sulphuric acid, Mercurous Sulphate, [>%>]= 2 =S0 2 , 



334 MERCURY. [§ 273. 

is formed; but if the heat be increased, and the evaporation 
carried to dryness, the first product is changed into Mercuric 
Sulphate, Ifg = 2 = S0 2 , which is a white crystalline powder, 
readily dissolving in a solution of common salt, but decomposed 
by pure water into a soluble acid and an insoluble basic salt. 
The last is known as turpeth-mineral. It has a yellow color, 
and its composition is expressed by the symbol, 

(Hg-0-Hg-0-Bg)-0fS0 2 . 

Mercurous sulphate is also prepared for the manufacture of 
calomel by triturating together mercuric sulphate with a quan- 
tity of mercury equal to that which it already contains. 

273. Sulphides. — Mercurous Sulphide, [Ifg^S, obtained 
as a black precipitate on passing U 2 S gas through the solution 
of a mercurous salt. Very unstable, like the corresponding ox- 
ide. Mercuric Sulphide (Vermilion, Cinnabar), HgS, is pre- 
cipitated by the same reagent from the solution of a mercuric 
salt. This precipitate is also black, but when sublimed the sub- 
stance acquires the peculiar vermilion tint. Vermilion is usually 
prepared by rubbing together mercury and sulphur, and sub- 
liming the black product. Crystals are frequently thus obtained 
identical in form with those of natural cinnabar (76). 

274. Chlorides. — Mercurous Chloride, \_Hg^ CI 2 , may be 
obtained either as a white powder or in crystals (75), — 1st. 
By subliming a mixture of mercuric chloride and mercury, 

Eg Ok + Eg = [Eg 2 -] Cl 2 . [306] 

2d. By subliming a mixture of mercurous sulphate and com- 
mon salt, 

\_Hg 2 ~\SO A + 2Na CI = Na 2 SO A + \_Hg 2 ~\ CI 2 . [307] 
3d. By precipitation from a solution of mercurous nitrate, 

{\_Hg 2 -\N 2 Q -f ZNaCl + Aq) = 

{_Hg 2 \d 2 + ($NaNO z -f Aq). [308] 

Calomel is insoluble in water, alcohol, and ether. The Sp. 
Gr. of its vapor is only one half of that which the theory would 
require, — an anomaly which is explained as an effect of disas- 



§276.] MERCURY. 335 

sociation. Sublimes below a red heat without melting. When 
triturated with a solution of soda or potash, it is turned black, 
owing to the formation of {Hg 2 ) 0, and when heated with alka- 
line chlorides it is converted into HgCl 2 . In the presence of or- 
ganic matter, acids, and air, this last change may take place, to 
some extent at least, at a temperature of 38° or 40°. Calomel 
is an invaluable medicine. It was first prepared by rubbing 
together in a mortar Hg -\- Hgd 2 , but this product, although 
having all the medicinal properties of the white sublimate, had 
a brilliant black color, whence the name, from ko\6s fxe\as. 

275. Mercuric Chloride (Corrosive Sublimate). HgCl 2 . — 
Crystalline (77) white solid, melting at 265°, boiling at 293°, 
and yielding a vapor whose Sp. Gr. (141.5) conforms very 
nearly to the theory. Soluble in water, alcohol, and ether. 
Forms salts with the alkaline chlorides as 2Na CI . Hg Cl 2 . May 
be prepared by subliming a mixture of mercuric sulphate and 
common salt, but adding a small amount of Ma 2 to the mix- 
ture to prevent the formation of calomel. Also found when 
mercury is burnt in chlorine gas. Coagulates albumen, and 
forms with it, as well as with other albuminoid substances, sta- 
ble compounds insoluble in water. Acts as a violent poison. 
Used for preserving from decay wood, dried plants, and other 
objects of natural history, and this effect appears to be due in 
part to its peculiar action on albuminoid compounds. It is also 
a valuable reagent, and is used to prepare other anhydrous 
chlorides. 

Mercury forms, like copper, a large number of oxichlorides. 
It also combines with the other members of the chlorine group 
of elements. Among these compounds the most interesting is 
the iodide, Hgl 2 , which affects two different crystalline forms dis- 
tinguished also by striking differences of color. As obtained 
by precipitation 

(HgCl 2 + 2KI+ Aq) = Hgl 2 + (2KCI + Aq), [309] 

it appears as a crystalline red powder (75). This when 
heated changes its crystalline condition (77) and becomes yellow, 
but the yellow variety is changed back to the red by mere 
friction. 

276. Ammoniated Compounds. — The compounds of mer- 



336 MERCURY. [§ 277. 

cury, when acted on by ammonia or its salts, yield a large num- 
ber of complex products. Among these the most remarkable 
is a powerful base called Mercuramine, which is formed by the 
action of aqua ammonia upon yellow precipitated oxide of mer- 
cury. There is a difference of opinion in regard to the arrange- 
ment of the atoms in this compound, but the most probable 

symbol is {Hg,{HgOH),mN)0-H . H 2 0. The hydrate ab- 
sorbs C0 2 from the air, and forms definite salts with all the 
common acids. This compound is unstable, but when heated, 
two molecules of the hydrate give up three molecules of water, 
and there is left a dark brown product permanent in the air, 
whose symbol may be represented after the type \_H A N] 2 0. 
The following are the symbols of a few only of the many mer- 
curial compounds of this class: — 

H 2 ,H 2 =N 2 \Hg 2 \ formed by the action of ammonia gas on pre- 
cipitated calomel. 
H 2 \^Hg 2 ^N 2 \Hg 2 \ black compound, formed from calomel by 

action of aqua ammonia. 
{H 2 ,H 2 ,Hg\N 2 -HgyCl 2 , *' White Precipitate," formed by adding 
to aqua ammonia a solution ot\HgCl 2 . 
(H 2 ,H 2 ,H 2 XN 2 -HgyCl 2 , "Soluble White Precipitate." 

277. Characteristic Reactions and Uses. — The salts of mer- 
cury, whether soluble or insoluble, are all reduced to the metal- 
lic state by a solution of stannous chloride. Any of the salts 
heated in a closed tube with sodic carbonate give a sublimate of 
minute globules of mercury. From solutions of its salts mer- 
cury is deposited as a gray film on metallic copper, and if short 
lengths of copper wire thus coated and carefully dried be heated 
in a closed tube, the sublimate is obtained as before. 

The chief consumption of metallic mercury is in the treat- 
ment of gold ores. It is also used for silvering mirrors, for 
making various philosophical instruments, and for other pur- 
poses in the arts. Large quantities are consumed in prepar- 
ing its various compounds, and these are among the most im- 
portant articles of the materia medica. 



* 
QUESTIONS AND PROBLEMS. 337 



Questions and Problems. 

1. Write the reaction of boiling sulphuric acid on copper. 

2. Write the reaction of nitric acid on copper, — 1st, assuming 
that NO is the aeriform product ; 2d, that it is N„0. 

3. Write the reaction which takes place when cupric nitrate is 
decomposed by heat. 

4. Why does not concentrated nitric acid act on copper ? 

5. Represent the constitution of the hydrate 4[Cw 2 ]0 .H o 0m the 
typical form. How may it be regarded as related to the normal 
hydrate [Cu 2 ]=#o 2 ? Ans. It equals 4[Cw 2 ]=/ft> 2 — 3H 2 0. 

6. How may anhydrous cupric sulphate be used to detect the 
presence of moisture ? 

7. In what other way may the symbols of the different basic sul- 
phates be written ? 

Ans. The symbol of Brochantite may be written (Cu-O-Cu-O- 
Cu-0-Cu)=0 2 =SO s . 3H 2 0, and the others in a similar way. 

8. How may the symbols of the basic sulphates be derived from the 
hydrates ? 

Ans. Disregarding the water of crystallization, we may regard Bro- 
chantite as formed from the condensed hydrate 4Cu=0 2 =H 2 
by first eliminating SH 2 and then replacing the remaining 
7/ 2 by SO r 

9. If the symbol of Brochantite is written as in the text, to what 
order of sulphates does it belong? Ans. Orthosulphates. 

10. Show by graphic symbols that the radical Cu0 2 H must be a 
monad. 

11. Represent by graphic symbols the composition of Malachite 
and Azurire. 

12. Both Malachite and Azurite may be regarded as formed by 
the mplecular union of cupric hydrate and cupric carbonate. Write 
the symbols on this theory. 

13. Malachite is how related to cupric hydrate ? 

Ans. It may be regarded as the hydrate doubly condensed with two 
of the hydrogen atoms replaced by CO thus, Cu=0=CO,H % 
or Cti=0 2 =CO . Cu=OfH„. Symbol of Azurite in the same 
way becomes Cu z Wi{CO\,H 2 or 2Cu=O^C0. Cu=OfH r 

14. To what order of carbonates does Mysorin belong? 

15 V 



338 QUESTIONS AND PROBLEMS. 

15. In "what other ways may the symbol of the cupric nitrates be 
written ? 

Ans. Cu*Of(NO& and Cu & W=NO^ or Cu--O n =(N0 2 ),H . Cu* 
0.fH r 

16. Write the symbol of dioptase in the same typical form. 

Ans. H & ,CuEOfSi 

17. To what order of silicates may dioptase be referred ? 

Ans. Orthosilicates. 

18. Wr'te the reaction of solution of sodic phosphate on solution 
of cupric sulphate. 

19. Represent the constitution of the various sulphides of copper 
by graphic symbols. 

20. In what relation does the fluohydrate of copper stand to the 
hydrate anil fluoride of the same metal? 

Ans. It holds an intermediate position, as shown by the symbols 
Cu=Ho 2 , Cu=Ho,Fl, CuFl 2 . 

21. Regarding the molecule of water in the common variety of 
Atacamite as water of constitution, how may the formula of this 
mineral be simplified? 

Ans. It may be halved and written (Cu-0-Cu)=Ho,Cl. 

22. How is Atacamite related to cupric hydrate ? 

Ans. 2Cu=Ho 2 = (Cu-0-Cu)=Ho a -4- H. 2 0, then replacing one 
atom of Ho in basic hydrate by CI. 

23. What do you find that is remarkable in the reaction of cupric 
hydride on hydrochloric acid ? Compare it with reaction [236], and 
consider whether it indicates a difference of condition in hydrogen 
similar to that in oxygen. 

24. Write the symbols of the ammonia compounds of copper in 
the vertical form. 

25. What evidence can you find that a portion of the nitrogen 
atoms in two of the compounds stand in a different relation to the 
molecule from the others? 

Ans. If the nitrogen atoms were all typical, we should expect the 
basic radicals to fix more than the equivalent of two univa- 
lent acid radicals. 

26. Write the symbols of the hydrates which correspond to the 
different basic nitrates of mercury, and show how such basic hy- 
drates may be derived from the assumed normal hydrates. 

27. How is it possible, that salts should exist corresponding to hy- 
drates that cannot be isolated ? 



QUESTIONS AND PROBLEMS. 333 

28. Show bow turpeth-mineral may be derived from an assumed 
normal hydrate. 

23. How would you seek to determine whether the black product 
obtained by grinding together Hg -j- 8 is a mixture or a compound ? 

30. By experiment it appears that the specific gravity of calomel 
vapor is 118.5. Wiiat should it be theoretically'.'' Into what is it 
probably decomposed when heated? Ans. 235.5; Ibj and II g CI 2 . 

31. In administering calomel as medicine, what associations with 
other drugs should be avoided ? 

32. How rrny calomel be distinguished from corrosive sublimate 7 

33. What is the theoretical Sp. Gr. of HgCl 9 and why should you 
anticipate so great a difference between it and the experimental re- 
sult ? 

Ans. 135.5. In such a dense vapor the deviation from Mariotte's 
law would probably be large. 

34. Write the reaction which takes place when a mixture of mer- 
curic sulphate and common salt are sublimed. 

35. In cases of poisoning by corrosive sublimate, why should milk 
or the white ofeggB be useful as temporary antidotes until the stomach 
can be emptied by an emetic or otherwise ? 

36. Write the symbols of the chloride, nitrate, sulphate, and car- 
bonate of mercuramine. 

37. Write the symbol of the oxide of mercuramine described 

above. 

38. Represent the different ammoniated compounds of mercury 
by vertical symbols, and point out the type of each. 



340 CALCIUM. §278.] 



Division F*. 

278. CALCIUM. Ca = 40. — Dyad. One of the most 
abundant and important constituents of the crust of the globe. 
The elementary substance is a soft, malleable metal, with a 
reddish tinge of color. Readily tarnishes in the air, and burns 
when heated, forming lime. Decomposes water at all temper- 
atures, forming calcic hydrate. 

2Ca + GXD = 2CaO. 
Ca+2ff 2 0=2Ca=Ho 2 + IE-m. L J 

The metal is obtained with difficulty either by the electroly- 
sis of the melted chloride or by decomposing the iodide with 
sodium. 

279. Calcic Carbonate. Ca^OfCO or Cao-CO. — The chief 
lime mineral. Remarkable for the great variety of its crystal- 
line forms. Dimorphous (Hexagonal and Orthorhombic). The 
hexagonal forms (Figs. 14, 16, 17, 40, 41, and 42) belong to 
the mineral species Calcite. The orthorhombic forms (74) to 
the species Aragonite. Sp. Gr. of Calcite 2.72, of Aragonite 
2.94. The last is also distinguished from the first by superior 
hardness, and falling to powder when heated. The crystalline 
varieties of calcite are readily recognized by a very striking 
rhombohedral cleavage. Limestones, Oolite, Chalk, Marble, 
Travertine, Tufa, Calcareous Marl, are names of varieties of 
rocks, which consist chiefly or wholly of one or the other of 
these two minerals, generally of calcite. Many of these rocks 
make excellent building stones. All the varieties of calcic 
carbonate dissolve with effervescence in dilute nitric and other 
acids, and may thus be distinguished from the siliceous miner- 
als which they sometimes outwardly resemble. Calcic carbonate, 
although nearly insoluble in pure water, is readily dissolved by 
water charged with C0 2 . Thus it is held in solution by the water 
of lime districts, and to a greater or less extent by most spring 
water. Such water, when strongly charged, deposits calcic car- 
bonate on exposure to the air, and thus are formed stalactites, 
tufa, and travertine. It also forms deposits in boilers, and de- 
composes the soap used in washing. (Hard water.) Calcic 
carbonate may be readily formed artificially by the reaction 



§282.] CALCIUM. 341 

(Ca Cl 2 + (NH^CO, + Aq) = 

Ca-CO z + (2(#2Q CZ + JLy). [311] 

Singularly, however, if the products of the reaction are boiled 
together, the reverse change takes place ; calcic chloride is 
formed, which dissolves, while ammouic carbonate is carried 
away with the steam. 

280. Calcic Oxide (Quick-lime). CaO. — Obtained by burn- 
ing limestone in kilns. 

Ca CO s = CaO + ©CD* [312] 

Amorphous white solid. Very infusible, and emitting an intense 
white light when ignited (Drummond Light). Has strong af- 
finity for water, and the chemical union is attended with the 
evolution of much heat (slaking). Exposed to the air, it grad- 
ually absorbs both water and carbonic anhydride (air slaking). 

281. Cakic Hydrate. Ca=Ho 2 . A light dry powder. Sol- 
uble in about 425 parts of cold water (lime-water). With a 
smaller quantity of water it forms a sort of emulsion called 
milk of lime, and with still less water it gives a somewhat 
plastic paste, which, mixed with sand, is ordinary mortar. 
Hydraulic cements, which harden under water, are made from 
limestones containing from fifteen to thirty-five per cent of 
finely divided silica or clay ; also by intimately mixing with 
chalk a due proportion of clay under regulated conditions, and 
subsequently burning. Calcic hydrate acts on the skin like a 
caustic alkali, and is used by the tanners for removing hair 
from hides. It has a strong affinity for C0 2 , and hence is used 
for rendering soda and potash caustic [97J. It is also em- 
ployed for purifying coal-gas, and in many other processes of 
the arts. It is largely used as a manure. Whitewash is milk 
of lime mixed with a little glue. 

282. Chloride of Lime or Bleaching Powder, CaOCl 2 , is 
formed by passing chlorine gas into leaden chambers containing 
slaked lime, which absorbs the gas very rapidly. 

CaO+ Cl-Cl— (Ca-0)-Cl 2 . [313] 

Very much used in the arts for bleaching cotton goods. The 
cloth having been well washed and digested in a weak solution 



342 CALCIUM. [§ 283. 

of chloride of lime, is passed into very dilute sulphuric acid, 
which liberates the chlorine in the fibre of the cloth. May also 
be used in the laboratory as a source of chlorine gas. 

(CaOCl 2 + H 2 SO, + Aq) = 

(Caso, + h 2 o -j- Aq) + m-m. pu] 

283. Calcic Peroxide. (Ca-0)=0. — Formed by adding 
H 2 2 to lime-water, but is a very unstable compound. 

284. Calcic Sulphate. Cu = 2 = SO i . — Second in importance 
of the lime minerals. It occurs in nature both in an anhydrous 
and hydrous form. The anhydrous mineral is called Anhydrite, 
the hydrous mineral is Gypsum. Anhydrite crystallizes in the 
orthorhombic system (77), and has Sp. Gr. = 2.9. Gypsum 
(CaS0 4 . 2H 2 0) crystallizes in the monoclinic system (Fig. 25), 
has Sp. Gr. = 2.3, and is softer than the first. Calcic sulphate 
is soluble in about 400 parts of water, and, like several of the 
lime salts, is much less soluble in hot water than in cold; and 
when water holding gypsum in solution is heated to a high tem- 
perature in steam-boilers, the whole is deposited in an insoluble 
condition (CaS0 4 . %H 2 0). It is a very common impurity 
of spring waters, and is another cause of their hardness, and of 
the crusts which they sometimes form on the inner surface 
of boilers. It is found in considerable quantity in the water of 
salt springs, and of the ocean. When these waters are evap- 
orated it is deposited before the common salt. Hence in nature 
we find that beds of rock-salt are usually associated with anhy- 
drite and gypsum. The last is by far the most abundant min- 
eral, forming in some places extensive rock deposits of great 
thickness. . It is, moreover, -found in beautifully transparent 
crystals (Selenite), which can be easily split into very thin 
plates, and it also forms the ornamental stone called alabaster. 
When heated, gypsum readily gives up its water of crystalliza- 
tion, and when not overburnt the dry product, if retlueed to 
powder and made into a paste, again unites with water and sets 
into a hard mass. This reunion, however, will not take {dace 
if the gypsum has been heated above 300° ; and anhydrite is 
then formed. The calcined gypsum, called Plaster of Paris, is 
used in immense quantities for making casts, and in various 
forms of stucco-work. Ground gypsum is also a valuable ma- 
nure, and finds other applications in the arts. 



§288.] CALCIUM. 343 

285. Calcic Phosphate. Cao s (PO) 2 . — The chief earthy con- 
stituent of the bones of animals. The animal obtains it from 
the plants, and the plant draws its supply from the soil. The 
grains of the cereals are especially rich in this bone-making 
material, and as the supply in the soil is usually limited, these 
plants, when cultivated year after year, soon exhaust it. Hence 
it is all important lor the agriculturist to restore to his laud the 
phosphates as fast as they are removed by the crops, and ground 
bones, guano, phosphorite, and other forms of calcic phosphate, 
are used for this purpose. The mineral Apatite is a crystal- 
line variety (Fig- 14) of this same material, but contains also 
about eight per cent of calcic fluoride mixed with more or less 
calcic chloride. lis symbol may be written (Ca 5 F)ixCyx(PO) 3 . 

286. Calcic Silicate (Tabular Spar), Cao=StO, is a not un- 
common mineral. Formed on the surface of the grains of sand 
when mortar hardens ; and the valuable qualities of hydraulic 
cements are probably due to a still more complete union of the 
same kind. An artificial stone of great strength may be made 
by first mixing together solutions of calcic chloride and sodic 
silicate, and then incorporating with the half-fluid mass a large 
proportion of sand. 

287. Calcic Fluoride (Fluor- Spar). CaF 2 . — An abundant 
mineral and the most important compound of fluorine. It is 
found both massive and crystallized in the forms of the isomet- 
ric system, generally in cubes. Has octohedral cleavage. The 
pure material is colorless, but the native crystals are frequently 
beautifully colored, and are among the most splendid specimens 
of our mineral cabinets. Exposed to the light, they frequently 
exhibit a rem irkable fluorescence, and many varieties of the 
mineral phosphoresce when heated. Although not very fusible 
by itself, fluor-spar forms a very fusible slag with gypsum and 
other earthy minerals frequently associated with lead ores. 
This property renders it a valuable flux in the process of smelt- 
ing such ores and hence the name fluor. In small quantities it 
is almost invariably associated with calcic phosphate, not only 
in the mineral kingdom, but also in the bones and teeth of 
animals. 

288. Calcic Chloride. CaCl 2 . — A deliquescent salt, readily 
obtained by dissolving calcic carbonate in hydrochloric acid. 
Also a secondary product in the preparation of ammonia [162], 



344 STKONTIUM. — BARIUM. [§289. 

CaC0 3 + (2RCI + Aq) = 

(CaCl 2 -\-H 2 + Aq)+ C0 2 . [315] 

A useful reagent, and also employed, on account of its hygro- 
scopic qualities, for drying gases. 

289. Calcic Nitrate. Cao=(N0 2 ) 2 . — Also a very soluble 
deliquescent salt, which is formed in the soil, in cellars, in lime 
caverns, and wherever organic matter decays in contact with 
calcareous materials. Chiefly important as a source of saltpetre. 

290. STRONTIUM, £r=87.6, and BARIUM, Ba = \37. 
— Dyads. The compounds of these elements are closely allied 
to the corresponding compounds of calcium, and the differences 
are only those which we should expect between members of the 
same chemical series. They are, however, far less abundantly 
distributed in nature. The most important native compounds 
are 

Strontic Carbonate, Strontianite, SrC0 3 , Sp. Gr. 3.70. 
Baric Carbonate, Witherite, BaC0 3 , Sp. Gr. 4.32. 

These are isomorphous with Aragonite. No hexagonal forms 
corresponding to calcite are known. In like manner we have 

Strontic Sulphate, Celestine, SrSO^ Sp. Gr. 3.95. 

Baric Sulphate, Heavy Spar, BaS0 4 , Sp. Gr. 4.48. 

These are isomorphous with anhydrite. No hydrous minerals 
corresponding to gypsum are known. Strontic sulphate is much 
less soluble in water than calcic sulphate, and baric sulphate is 
practically insoluble. Moreover, the solubility of these salts is 
not increased by the presence of weak acids. Hence a solution 
of calcic sulphate will give a precipitate in solutions containing 
either strontium or barium, and a solution of strontic sulphate 
only in the last. The sulphates are both easily prepared artifi- 
cially from solutions of corresponding chlorides by precipitation 
with sulphuric acid. 

291. The Strontic and Baric Nitrates and the Strontic and 
Baric Chlorides are all soluble salts, but less soluble than the 
corresponding salts of calcium, the barium compounds being in 
each case the le-s soluble of the two. They are easily prepared 
by dissolving the native carbonates in dilute nitric or hydro- 






§295.] STBONTIUM.— BARIUM. 345 

chloric acids. Baric nitrate is precipitated from its aqueous 
solution by strong nitric or hydrochloric acid in consequence of 
its sparing solubility in these reagents. They may also be pre- 
pared from the native sulphates, as is illustrated by the folio w- 



SrSOt + 4(7 = SrS+ 4@®. 

[316] 

(SrS + 2HCI + Aq) = (SrC% + Aq) + m& 

An intimate mixture of the powdered sulphate with some car- 
bonaceous material is first intensely heated in a crucible. The 
resulting product is then exhausted with water, and the solution 
treated with hydrochloric or nitric acid as required. 

292. Strontic and Baric HydraUs may also be prepared 
from the solution of the sulphides, obtained as above, by the 
reaction 

0u + (BaS +B,0 + Aq) = 

CuS+ {Ba-Ho 2 -\- Aq). [317] 

The relative solubility of the hydrates follows the inverse order 
of that of the other salt-, baric hydrate being much the most sol- 
uble and dissolving in twenty parts of water. 

29-'3. Strontic and Baric Oxides may be readily obtained by 
igniting the nitrates. They slake when mixed with water, like 
quick-lime. 

294. Strontic and Baric Peroxides are prepared by heating 
the oxides in an atmosphere of oxyg-m gas. They are more 
stable than calcic peroxide, and baric peroxide is an important 
reagent. 

235. Characteristic Reactions. — Calcium, strontium, and 
barium are all precipitated from their solutions by alkaline car- 
bonates and by oxalic acid. They may be distinguished from 
each oilier by the relative solubility of their sulphate-, 1 and by 
the colors of their flames, which show characteristic bands with 
the spertro-cope. The compounds of strontium impart to a 
colorless flame a brilliant crimson color, and those of barium a 

1 Calcic sulphate gives an instantaneous precipitate in solutions of barium 

salts, while in those of stroutium the precipitate Ouly forms after a perceptible 
interval of time. 

15* 



346 LEAD. [§296. 

yellowish green. Hence they are much used by makers of fire- 
works. The soluble salts of barium are important reagents in 
the laboratory, and both the native and the artificial sulphate 
furnish an important white paint. 

296. LEAD. Pb = 207. Bivalent or quadrivalent. One 
of the more abundant metallic elements, found chiefly in mineral 
veins. Principal ore is Galena, PbS. There is also a native 
Plumbic Carbonate called Cerusite (PbC0 3 , Sp. Gr. 6.48), 
isomorphous with Aragonite, and a native Plumbic Sulphate 
called Anglesite (PbSO±, Sp. Gr. 6.30), isomorphous with an- 
hydrite. 

297. Metallic Lead. Pb? — Sp. Gr. 11.36. Melting-point, 
325°. So soft that it can be moulded by pressure. Obtained, 
1st. By alternately roasting and melting the galena in a rever- 
beratory furnace. 

Roasting stage, 

3PbS+ 30-0 = PbS +2PbO + 2^® 2 ,or 
2PbS -[- 20-0 = PbS + PbSO i; t ol8 -l 

Melting stage, PbS + 2PbO = 3Pb + g® 2 . or 

PbS + PbSO, = 2Pb + 23 © 2 . l 319 J 

2d. By smelting the galena with scrap-iron in a blast-furnace, 

PbS + Fe = FeS -f Pb. [320] 

Practically, nowever, both processes are far more complex thp,;i 
the reactions would indicate. The ore is in all cases mixed with 
gangue, which can only be melted with the aid of some flux, 
and the slags thus formed contain a large amount of metal and 
must be smelted again. 

Lead dissolves readily in dilute nitric acid, but is not acted 
on, or only very slightly, by either hydrochloric or sulphuvic 
acids, unless concentrated and boiling. Employed in number- 
less ways in the arts, both pure and alloyed, with other metals. 
Type-metal, bn'tannia-metal, and solder are among the most im- 
portant of its alloys. 

298. Plumbic Oxide. PbO. — Obtained bv heating Wd in a 
current of air, when, if the heat is not too great, a yel'ow pow- 
der is obtained called Massicot. At a heat a little below red- 



§ 302.] LEAD. 347 

ness the oxide melts and crystallizes on cooling in yellowish 
red scales called Litharge. Largely used in the arts for mak- 
ing flint-gla>s, for glazing earthenware, and for preparing vari- 
ous paints aud lead salts. 

299. Plumbic Peroxide. Pb0 2 . — A dark -brown powder, 
very useful in the laboratory as an oxidizing agent. The bright 
red powder called Minium, obtained by still further roasting 
massicot at a low red heat, is a mixture of Pb0 2 and PbO. 
There is al<o a suboxide, Po 2 0. 

300. Plumbic Hydrate. — The normal hydrate, Pb=Hb 2i has 
never been obtained, but we can readily form 

Diplumbic Hydrate (Pb-0-Pb)=Hn 21 

Triplumbic Hydrate \pb-0-Pb-0-Pb)--Ho^ 

by the following reactions : — 

2Pb=(NO,) 2 + (AK-Bo -f Aq) = 

(Pb-0-Pb)-Ho 2 + {AK-N0 3 + H 2 + Aq). [321] 

((Pb 3 2 )=(C 2 II 3 2 ) 2 + 2(Nff 4 )-iro+Aq) = 

(Pb 3 2 )=M 2 + {2{NH,)-(C 2 H 3 0. 2 ) +Aq). [322] 

A plumbic hydrate is formed by the simultaneous action of 
air and water on lead, which is slightly soluble ; and as all lead 
salts are poisonous, and even in minute quantities, if the dose is 
often repeated, miy be injurious to health, it is not safe to use, 
for drinking, water which has been kept in cisterns lined with 
lead or drawn through lead pipes. The presence of nitrites, 
nitrates, or chlorides greatly increases the corrosive action of 
water on lead, while carbonates and sulphates exert a preser- 
vative influence. 

301. Plumbic Nitrate. Pb={NO ? ) 2 . — Obtained by dissolving 
litharge or lead in dilute nitric acid. Soluble in water, but in- 
soluble in strong nitric acid. 

PbO+ (2H-N0 3 + Aq) == (Pb-(N0 3 ) 2 +If 2 0+Aq). [323] 

3Pb + (SH-N0 3 -f A 7 ) = 

(SPb-(N0 3 ) 2 4-4^0 + Aq) -f 225*©. [324] 

302. Plumbic Acetate (Suyar of Lead). Pb-(C 2 II 3 2 ) 2 . 



348 LEAD. [§303. 

3H 2 0. — The most important soluble salt of lead, easily ob- 
tained by dissolving PbO in acetic acid. Lead has a great 
tendency to form basic salts (38). Hence a solution of the 
neutral acetate will dissolve a large additional quantity of 
litharge. 

2Ph© + {Pb-{C 2 H,0 2 ) 2 -\- M) = 

((Pb-0-Pb-0-Pb)=(C 2 H 3 2 ) 2 -{- Aq). [325] 

If C0 2 is now passed through this solution, the excess of PbO 
is precipitated as carbonate. Fresh portions of PbO may then 
be dissolved and the process repeated. The plumbic carbonate, 
which is obtained by this and other analogous methods, is very 
much used as a white paint under the name of white lead. The 
products of the different processes have not, however, the same 
composition, but are mixtures of the carbonate and hydrate in 
varying proportions. 

303. Plumbic Sulphate, PbS0 4 , is obtained as a white pre* 
cipitate on adding sulphuric acid or a soluble sulphate to a solu- 
tion of a salt of lead. It is practically insoluble in pure water 
and dilute sulphuric acid. 

304. Plumbic Phosphate is found in nature in the mineral 
Pyromorphite, which is isomorphous with apatite and has an 
analogous constitution (Pb 5 Cl)ixO d \x(PO) 3 . The mineral Mim- 
etine is the corresponding isomorphous arseniate. A melted 
globule of plumbic phosphate assumes on cooling a peculiar 
radiated crystalline structure, which is very characteristic. 

305. Plumbic Chloride, PbCl 2 , may be obtained as a white 
crystalline powder by the reactions 

PhO + (2RCI + Aq) = PbOl 2 +(H 2 + Aq). [326] 
{Pb(N0 3 ) 2 + 2HCI + Aq) = 

PbCl 2 -f {2HNO, + Aq). [327] 

It is only very slightly soluble in cold water, but in boiling 
water dissolves quite readily. 

306. Plumbates. — Caustic alkalies dissolve Pb O very freely, 
forming salts in which the lead plays the part of a negative 
radical. Hence the precipitate formed in reaction [321] dis- 
solves in an excess of the reagent, and a solution of PbO in 
lime-water is used as a hair-dye. 



§307.J REACTIONS AND PROBLEMS. 349 

307. Characteristic Reactions. — The lead compounds, in 
many of their reactions, are closely allied to the compounds of 
the first three elements of this group. For example, the sol- 
uble salts give precipitates with the alkaline carbonates and 
with oxalic acid. But in other reactions there are marked dif- 
ferences. Thus, 1. A strip of metallic zinc placed in a solution 
of plumbic acetate precipitates all the lead. 

Zn + (Pb-(CAO,) 2 + Aq) = 

Pb + {Zn-{C 2 H,0^ 2 + Aq). [328] 

2. Sulphuretted hydrogen gas passed through either an acid or 
an alkaline solution of a salt of lead gives a black precipitate of 
plumbic sulphide. 

(Pb=Cl 2 + ff a S + Aq) = PbS + (2HCI + Aq). [329] 

When the solution is acidified with hydrochloric acid, the pre- 
cipitate is first red, owing to the formation of (Pb-S~PbyCl 2 , 
but this is soon converted into the black sulphide. 3. Heated 
on charcoal before the blow-pipe, with reducing fluxes, the 
compounds of lead yield a soft, malleable bead of metal, and the 
charcoal immediately around the bead is at the same time 
coated with an incrustation of oxide which is orange-colored 
while hot, but becomes lemon-yellow when cold. By these 
reactions lead is easily distinguished from calcium, strontium, 
and barium. Indeed, the distinction is so marked, that, al- 
though the resemblances are very striking, it may be doubted 
whether lead belongs to the same chemical series. 



Reactions and Problems. 

1. Calcite and Aragonite are both not unfrequently found in acic- 
ular crystals. How may they be distinguished ? 

2. Compare the molecular volumes of Calcite and Aragonite. 

3. By igniting 100 parts of pure calcic carbonate, Dumas obtained 
exactly 56 parts of lime. What is the atomic weight of calcium ? 

Ans. 40. 

4. What assumptions are made in the last problem ? (19.) 



350 REACTIONS AND PROBLEMS. 

5. How much CaO can be obtained from 100 kilogrammes of pure 
limestone? How much Ca=Ho 2 will this amount yield? 

Ans. 56 kilos, and 74 kilos. 

6. How much limestone must be burnt to yield 560 kilos, of quick- 
lime ? How many cubic metres of C0 2 would be set free in the 
process? Ans. 1,000 kilos, and 223.1 m. 8 

7. In one cubic metre of limestone assumed to be pure calcic car- 
bonate, Sp. Gr. 2.72, how many cubic metres of C0 2 are condensed? 

Ans. 607.1 m. 8 

8. What is the cause of the incrustation of boilers by calcic car- 
bonate ? 

9. Lime-water is used to purify hard water. Explain the reaction. 

10. A bed of limestone, Sp. Gr. = 2.75, and 100 metres thick, 
would make a bed of anthracite coal of what thickness? Assume 
that the Sp. Gr. of anthracite is 1.8, and that it contains 90 per cent 
of carbon. Ans. 20.37 metres. 

11. In order to precipitate lime as completely as possible with 
ammonic carbonate, it is important to avoid an excess of ammonia 
salts, and to warm the liquid, but not to boil it. Give the reasons 
for these precautions. Also analyze reactions [311 and the reverse], 
and state the principle under which they may be brought. 

12. One cubic decimetre of quick-lime, Sp. Gr. 3.18, will absorb 
how many cubic decimetres of water ? How many units of heat will 
be evolved by the change of state which the water undergoes ? 

Ans. 1.022 dTS: 8 

13. In burning quick-lime it is found that the process succeeds 
best in damp weather, and is facilitated by injecting steam into the 
kiln. Why should you infer that this would be the case? (58.) 

14. Give an explanation of the hardening and adhesion of mortars 
and cements. 

15. When milk of lime is spread over walls in the process of white- 
washing, what compound is formed on the surface ? 

16. How many cubic metres of CO % can be absorbed by a quan- 
tity of milk of lime, containing 112 kilos, of lime (CaO)? 

17. When lime-water is shaken up with C0 2 it is rendered turbid. 
How do you explain the reaction, and to what application of lime- 
water in the laboratory does it point ? 

18. In order to render 100 kilos, of sal soda caustic how much 
quick-lime must be used? [97.] Ans. 52.83 kilos. 

19. How many litres of chlorine gas would be absorbed by 100 



REACTIONS AND PROBLEMS. 351 

kilos, of lime (CaO) first reduced to hydrate, and how much MnO t 
must be used to yield the requisite amount ? 

Ans. in part, 39.85 litres of chlorine. 

20. Bleaching salts have been regarded as a mixture of calcic 
chloride with calcic hypochlorite. How would you write the symbol 
on this theory ? 

21. Kepresent by graphic symbols CaCO a , Ca0 2 , CaOCl r 

22. The percentage composition of gypsum is calcium, 23.26 ; sul- 
phur, 18.61 ; oxygen, 37.21 ; water, 20.92. Calculate the symbol. 

23. Is the incrustation of steam-boilers by insoluble calcic sulphate 
due to the same cause as the incrustation of salt-pans by gypsum ? 
Explain the difference. 

24. If the calcium contained in one cubic decimetre of anhydrite 
could be replaced by H 2 , what would be the volume of the product 
formed ? 

25. If a concentrated solution of sodic sulphate is mixed with a 
concentrated solution of calcic chloride, the whole mass becomes 
solid. Write the reaction, and explain what becomes of the water 
of solution. 

Ans. (Na^SO, + CaCl 2 + 2H 2 0) = 2NaCl + CaSO, . 2H 2 0. 

26. How could you detect the presence of sulphuric acid and lime 
in a solution of gypsum? Write the reactions 

27. Represent the constitution of apatite by a graphic symbol. 

28. How may you regard apatite as derived from calcic hydrate ? 
What important part does fluorine play in the compound V Does 
not the presence of such a univalent element" in this compound fur- 
nish an argument in favor of the diatomicity of calcium ? 

29. How much hydrochloric acid, Sp. Or. 1.1, will be required to 
dissolve 50 grammes of chalk, and how many litres of @ © 2 could be 
thus obtained ? 

Ans. 179 grammes of acid and 11.16 litres of C0 2 . 

30. By what single reaction could you change a solution of calcic 
nitrate into a solution of nitre? 

31. What evidence do you find in this section that calcium is 
bivalent ? 

32. Compare the molecular volumes of the native carbonates of 
strontium, barium, and lead with those of Aragonite and Calcite. 

33. Write the reactions by which strontic and baric sulphates may 
be prepared from the corresponding nitrates or chlorides. 

34. Analyze the reactions by which the chlorides and nitrates of 



352 REACTIONS AND PROBLEMS. 

strontium and barium mav be prepared from the corresponding sul- 
phates, and show why such a circuitous method is necessary. 

35. Compare the molecular volume of the sulphates of this group 
with that of the corresponding carbonates. 

36. How may solutions of calcic and strontic sulphates be used 
to detect barium and strontium, even if mixed together in the same 
solution ? 

37. Knowing that sulphuric acid if in excess will completely pre- 
cipitate barium and strontium, how can you detect the presence of 
lime in a solution containing all three ? 

38. On what does the use of the salts of barium as tests for sul- 
phuric acid depend ? 

39. To how much SO s do 0.932 grammes of baric sulphate cor- 
respond? Ans. 0.320 grammes. 

40. A quantity of Witherite weighing 0.591 grammes was dissolved 
in hydrochloric acid and precipitated with sulphuric acid. The pre- 
cipitate when washed, dried, and ignited weighed 0.G99 grammes. 
What per cent of barium does the mineral contain ? 

Ans. 69.37 per cent. 

41. Baric and strontic carbonates are not, like calcic carbonates, 
easily decomposed when heated in the air, but readily give off C0 2 
if heated in an atmosphere of hydrogen. Plow do you explain these 
facts ? and do they confirm or otherwise your answer to question 13 ? 

42. "What is the percentage of lead in the three minerals Angle- 
site, Cerusite, and Galena? Ans. 68.32, 77.54, 86.62. 

43. Analyze reactions [318-320] and state the general theory of 
the smelting process, including the removal of the gangue and the 
reduction of the ore. 

44. Explain the peculiar action of lead with acid solvents. Why 
must the nitric acid be diluted, and to what extent ? 

45. How many kilos, of litharge can be obtained from 37.1 kilos, 
of lead, and what volume of oxygen gas would be absorbed in the 
process ? Ans. 39.96 kilos, and 2 m. 3 

46. Represent the plumbic oxides and hydrates by graphic sym- 
bols, and show how the basic hydrates are related to the assumed 
normal hydrate. 

47. The action of nitric acid on lead depends on the degree of 
concentration and on the temperature. Write the reaction assuming 
that N 2 is formed. 

48. How many kilos, of crystallized sugar of lead can be made 
from 6.69 kilos, of litharge? Ans. 11.37 kilos. 



KEACTIONS AND PROBLEMS. 353 

49. How much litharge will a solution containing 11.37 kilos, of 
sugar of lead dissolve, assuming that triplumbic acetate is the product 
formed? Ans. 13.17 kilos. Pb 0. 

50. Write the reaction of CO„ on a solution of basic acetate of 
lead. 

51. How may the basic acetates be regarded as derived from the 
normal hydrates ? 

52. Write the reaction of dilute sulphuric acid on a solution of 
plumbic nitrate. 

53. Represent the constitution of pyromorphite and mimetene by 
graphic symbols. 

54. What is the derivation of the name pyromorphite ? 

55. Will the whole of the lead be precipitated from its solution in 
acetic acid by an excess of HCl -f- Aqf 

56. By what reagent may you precipitate the whole of the lead 
from a solution of one of its salts ? 

57. Why should a solution of PbO in lime-water blacken the hair 
or any other organic material containing sulphur? 

58. How could you detect the presence of lead in water ? 

59. From a solution containing all the members of this group, how 
could you separate the whole of the lead ? 

60. The solubility of the compounds of the elements of this group 
diminishes, as a general rule, in proportion as the atomic weight of 
the metallic radical increases. Does this fact conform to the law 
which generally obtains in chemical series in regard to the chemical 
energy of the different members ? 



354 MAGNESIUM. [§ 308. 



Divisions VI. and VII. 

308. MAGNESIUM. Mg — 24. — Dyad. One of, the 

most widely distributed elements, although not so abundant as 
Calcium, with which it is usually associated. In some of its 
relations it is very closely allied to calcium, but also differs 
from it in many important respects. 

309. Metallic Magnesium, Mg, is readily obtained by decom- 
posing the anhydrous chloride with metallic sodium, also by 
electrolysis. It is a silver-white metal, melting at a red heat, 
and volatilizing at a high temperature in an atmosphere of hy- 
drogen. It is malleable and ductile, is susceptible of a high 
polish, and does not tarnish in dry air. Heated in the air it 
takes fire and burns with great splendor [59], and it is now 
much used as a source of pure white light when great bril- 
liancy is required. Boiling water acts upon the metal quite 
rapidly, but it decomposes cold water only very slowly. 

3 1 0. Magnesic Oxide ( Calcined Magnesia), Mg 0, is obtained 
when the metal is burnt in air. It can also be obtained by cal- 
cining the carbonate or the nitrate. It is a bulky white powder, 
wholly infusible, and emitting a bright white light when heated 
before the blow-pipe. Intensely heated, it appears to volatilize 
unchanged. When mixed with w r ater it slowly unites wilh it 
to form a hydrate. The oxide obtained by calcining the nitrate 
is much denser than that marie from the carbonate, and possesses 
remarkable hydraulic qualities. When mixed with water, it 
soon sets forming a hard compact mass resembling marble. If 
the oxide is heated to a very high temperature, it loses its power 
of uniting with water, and dissolves only slowly even in the strong- 
est acids. Crystallized MgO (Figs. 5 to 7), Periclase, has been 
found in small grains imbedded in a limestone rock ejected from 
Vesuvius, but otherwise it does not occur uncombined in nature. 

311. Magnesic Hydrate, Mg :z 2 =H 2 , is found native, crystal- 
lized in large hexagonal plates (76), Brucite. It can be read- 
ily formed artificially as above, also by adding caustic potassa, 
soda, or baryta to the solution of any of its salts. It is but 
very slightly soluble in water, yet sufficiently to give a distinct 
alkaline reaction (39). It absorbs G0 2 slowly from the air, but 
much more slowly than calcic hydrate. 



§313.] MAGNESIUM. 355 

312. Magnetic Carbonate. 31g=0.fC0. Sp. Gr. 3.056.— 
The mineral Magnesite, isomorphous with Calcite. Insoluble 
in pure water, but in carbonic acid water more soluble than 
calcic carbonate. This solution is much used as a medicine 
(liquid magnesia). If exposed to the air, the magnesic car- 
bonate slowly separates in crystalline flakes, containing three 
atoms of water. Anhydrous magnesic carbonate is not readily 
obtained artificially. The precipitate obtained on adding to a 
boiling solution of a magnesia salt sodic carbonate is a mixture 
of magnetic carbonate and magnesic hydrate in variable pro- 
portions (Magnesia Alba). The product, however, appears to 
be rather a mixture of several definite compounds of these two 
salts ; and a crystalline mineral is known called Hydromagnesite, 
which has the formula II i Mg 4 12 C 3 . 2H 2 or 

IV 

Ho^(C=MgofC-MgofC) . 2ff 2 0. 

Magnesic carbonate is found united with calcic carbonate in 
the mineral Dolomite (Sp. Gr. 2.9). This is by far the most 
abundant native compound of magnesium, and forms in many 
localities extensive beds of rocks. It occurs in large and well- 
defined crystals which are isomorphous with calcite and magne- 
site (Fig. 16). The mineral is somewhat variable in its com- 
position, and may either be regarded as an isomorphous mixture 
of these two substances, or else as a definite compound mixed 
with an excess of one or the other of its constituents. 

Mg CO., + Ca C0 3 or Mgo-( C- 2 =0)= Cao. 

When calcined at not too high a temperature, the ma<rnesic car- 
bonate is alone decomposed, and a product obtained which forms 
an excellent hydraulic cement. From the calcined mass the 
magnesia can be dissolved out by carbonic acid water and freed 
from the lime. In this way pure magnesic carbonate is pre- 
pared. 

313. Magnesic Sulphate (Epsom Salt). MgS0 4 . 1R 2 0. — 
The most important soluble salt of magnesia. Obtained from 
the bittern of sea-water, or by treating the native carbonates or 
Dolomite with sulphuric acid. It is a very common ingredient 
of mineral waters, like those of Epsom, and is formed when 
water saturated with gypsum filters through Dolomitic rocks. 



^56 MAGNESIUM. [§314. 

The salt, with seven molecules of water, is dimorphous, crystal- 
lizing both in orthorhombic forms isomorphous with ZnS0 4 . 
7HO, and in monoclinic forms isomorphous with FeSO i . 7 HO. 
It may al.-o be obtained crystallized with 1, 2, 3, .... 12 mole- 
cules of water under regulated conditions, chiefly of temperature. 
The compound 3fgS0 4 . H 2 (Kieserite) is found in the Stass- 
furt salt-beds. Epsom salt is reduced to the same composition 
when heated to 150°, but the last molecule of water is retained 
even at 200°, and this leads us to believe that it forms a part 
of the molecule of the salt, whose formula would then be writ- 
ten, Mgo=SO=Ho ii This opinion is confirmed by finding that 
this molecule of water may be replaced by the molecule of an 
alkaline sulphate, forming a double salt, which crystallizes with 
6II 2 in the same form as magnesic sulphate with 1H 2 0. The 
symbol of the potash salt is 

Mgo=(SO*0 2 =OSyKo 2 . 6^0. 

Epsom salt dissolves in about three times its weight of cold 
water. It is a valuable medicine, but, like all the soluble salts 
of magnesium, it has a bitter, disgusting taste. 

314. Magnesic Silicates. — The well-known minerals, Ser- 
pentine, Talc (Soap-Stone), and Chrysolite (Olivine), are es- 
sentially magnesic silicates; and in many other native silicates, 
including the Hornblendes, Augites, Chlorites, and some vari- 
eties of Mica, magnesium is one of the principal ba>ic radicals. 

315. Magnesic Chloride. MgCl 2 . — Found dissolved in sea- 
water, and the cause of its bitter taste. Obtained by dissolving 
magnesic carbonate in hydrochloric acid, and evaporating in an 
atmosphere of hydrochloric acid gas. If evaporated in the air, 
the salt is partially decomposed. Very fusible. Used for making 
magnesium. Forms double salts with alkaline chlorides (134). 

316. Characteristic Reactions. — Magnesium, although 
closely related to calcium, is distinguished from the alkaline 
earths by the great solubility of its sulphate, also by its ten- 
dency to form soluble double salts with ammonium, in conse- 
quence of which no precipitate is formed in solutions of its salts 
either by ammonia or ammonic carbonate, when sufficient excess 
of some ammonia salt is present. The ammonic magnesian 
phosphate, however, (NII 4 ) 2 ,Mg 2 iO (i lP 2 2 . Y2H 2 is insoluble, 
and is formed whenever sodic phosphate is added to an am- 
moniacal solution of a magnesium salt. This reaction furnishes 
the most delicate test for magnesium salts. 



§320.] ZINC. 357 

317. ZINC. Zn = 65.2. — Dyad. One of the more abun- 
dant metallic elements. The principal ores are 

Red oxide of Zinc 1 ZnO Hexagonal, 

Blende ZnS Isometric, 

Smithsonite Zno = CO Hexagonal, 

Calamine Zno 2 =Si .2H 2 Trimetric. 

The ores are reduced by first roasting or calcining until the 
metal is in the condition of an oxide, and then distilling with 
a mixture of coal in earthen retorts or muffles. 

318. Metallic Zinc. Zn. — Sp,Gr. 6.8 to 7.2. Fuses at 
500°. Boils at a red heat. The polished surface has a bright 
lustre, with a bluish tint, but soon tarnishes in moist air. Has 
a crystalline structure, but, although brittle both at a high and 
a low temperature, it may readily be rolled out into sheets at a 
temperature of about 140°. Sheet-zinc is nearly as cheap as 
sheet-iron ; and since it does not rust, or at most only very su- 
perficially, it is preferable for many purposes. Iron, however, 
is a much stronger metal, and is frequently coated with zinc to 
protect it from rusting. It is then said to be galvanized. Zinc 
readily dissolves in dilute acids with the evolution of hydrogen, 
and is much used in the laboratory, together with dilute sul- 
phuric acid, for making this gas. The metal is first granulated 
by pouring it, when melted, into water. When boiled with a 
solution of caustic soda or potash, it also dissolves with evolution 
of hydrogen. 

Zn + (2JKo-JI+ Aq) = (Ko 2 =Zn + Aq) + HI-HI. [330] 

It is used as the electro-positive metal in the galvanic battery. 

319. Zincic Oxide, ZnO, which is made in large quantities 
by burning zinc vapor at the mouth of the reduction furnaces, 
is a very light white powder, much used, when mixed with oil, 
as a white paint. A denser oxide is obtained by calcining 
zincic nitrate. 

320. Zincic Hydrate, Zn=Ho 2 , is formed by the reaction 

(ZnSO, + 2K-Ho + Aq) = Zn-Ho 2 + (K 2 S0 4 + Aq), [331] 
but is soluble in an excess of reagent. 

1 The color is due to the presence of a small amount of manganese. 



358 ZINC. [§321. 

321. Zlncic Carbonate, ZnC0 8 , is isomorphous with magne- 
site and calcite. When prepared by precipitation, a mixture of 
hydrate and carbonate is formed, as in (312). 

322. Zlncic Sulphate {White Vitriol). ZnS0 4 .7H 2 0.—Yery 
soluble salt, isomorphous with Epsom salt, which it closely re- 
sembles in most of its chemical relations, forming similar double 
salts. Preparation as in [64]. Used in pharmacy. 

323. Zlncic Chloride. ZnCl 2 . — A solution of zinc in hydro- 
chloric acid can be concentrated by evaporation without decom- 
position. All the water is not driven off until the temperature 
reaches 250°. The result is a thick syrup, which forms, on 
cooling, a white, deliquescent solid, melting at 100°, called by 
the alchemists Butter of Zinc. It has an intense affinity for 
water, and by its aid the elements of water may frequently be 
removed from a chemical compound without producing any 
further change. Thus, alcohol may be converted by it into 
ether or ethelyne. According to the proportions used, we have 

C 2 ff Q 0—ff 2 = C 2 ff 4 or 2C 2 H Q 0—If 2 0=2C 2 H 5 0. [332] 

Ethylene. Ether. 

For the same reason it acts as a cautery on the skin. It is 
also used in solution as an antiseptic and disinfecting agent. 

324. Zinc and the Alcohol Radicals. — Zinc M^thide, 
Zn--{CHz) 2 . ZincEth"de,^=((7 2 i7 5 ) 2 ; ZincAmylide^^CyZ^. 
Observed £p. (@>r. of vapor, 3.29, 4.26, and 6.95 respectively. 
Obtained both by heating zinc with the iodides of methyl, ethyl, 
or arnyl in sealed tubes, and by the action of zinc on the mer- 
cury compounds of the same radicals. They are all three 
colorless, transparent, strongly refracting, and mobile liquids. 
They are also volatile, boiling at the temperatures of 46°, 1 18°, 
and 220° respectively. They are, likewise, highly inflammable, 
and the first two take fire spontaneously in the air. As these 
compounds do not, as a whole, combine with any of the ele- 
ments, their molecules are evidently saturated, and they are 
interesting as fixing beyond all doubt the atomic relations of 
zinc. Moreover, they are useful reagents in many processes 
of organic chemistry. 

325. Characteristic Reactions. — Zinc, like magnesium, 
forms soluble double salts with ammonia, but it is easily distin- 
guished by the fact that its sulphide is insoluble, not only in 



§326.] INDIUM. — CADMIUM. 359 

solutions of the fixed alkalies, but also in those of ammonia and 
its salts. Hence it is precipitated from all alkaline solutions by 
sulphuretted hydrogen. The sulphide thus obtained is a white 
precipitate, soluble in dilute mineral acids, but insoluble in 
acetic acid. 

326. INDIUM. In = 72. Sp. Gr. 7.42. CADMIUM. 
Cd= 112. Sp. Gr. 8.69. — Dyads. Two rare metallic ele- 
ments associated with zinc. Indium only in exceedingly mi- 
nute quantities, and at very few localities. Cadmium far more 
generally, and in much larger amounts. Indium is less vola- 
tile, and cadmium more volatile, than zinc, and hence in distill- 
ing zinc from its ores the cadmium is found in the "zinc dust" 
which is collected in the early stage of the process, while the 
indium comes over later with the great mass of the zinc, with 
which it remains alloyed. With sufficient differences to mark 
their individuality, these metals resemble zinc in almost every 
particular. They form similar oxides and hydrates, similar sol- 
uble salts with hydrochloric, nitric, and sulphuric acids, similar 
soluble compounds with ammonia salts, similar light-colored sul- 
phides insoluble in alkaline solutions and acetic acid. Cadmi- 
um differs from the others in this respect, that its hydrate is 
insoluble in caustic soda or potash, its basic carbonate insoluble 
in excess of ammonic carbonate, and its yellow sulphide insolu- 
ble in dilute mineral acids. This sulphide is found in nature, 
and the mineral is called Greenockite. Zinc precipitates cad- 
mium from solutions of its salts, and both zinc and cadmium 
precipitate indium. Indium and cadmium are more fusible than 
zinc, and form very fusible alloys. Indium melts at 176°, cad- 
mium at 242°, and an alloy of cadmium with lead, tin, and bis- 
muth has been made which melts at 60°. Cadmium boils at 
860°, and the Sp. Gr. of its vapor has been found by obser- 
vation to be 56.85. Indium and cadmium burn when heated 
before the blow-pipe, the first yielding a yellow, and the last 
a brown oxide, very unlike the white oxide of zinc. Although 
so closely allied to magnesium and zinc, these associated ele- 
ments probably belong to a different although parallel series, 
and the relation between the atomic weights of the four ele- 
ments is in harmony with this view. All these four metals 
show very characteristic bands with the spectroscope, and in- 
dium was first discovered by the well-marked indigo-blue band, 
from which it takes its name. 



360 QUESTIONS AND PROBLEMS. 



Questions and Problems. 

1. Write the reaction of sodium on magnesic chloride. 

2. When water is decomposed by magnesium, what are the prod- 
ucts? Write the reaction. [43.] 

3. How do you account for the intense brilliancy of the light 
emitted by burning magnesium ? (95.) 

4. Write the reaction of water on calcined magnesia. [45.] 

5. Write the reaction of solution of caustic soda on solution of 
magnesic chloride. 

Ans. (MgCl z + 2NaHo + Aq) = MgHo. z -f- (2NaCl + Aq.) 

6. Represent the composition of hydromagnesite by graphic 

symbols. 

7. Represent, graphically, the compound radicals Mgo, Cao, Zno, 
and show their relations to hydroxy 1. 

8. Represent, graphically, the composition of Dolomite. 

9. What do you understand by the term isomorphous mixture ? 

10. Explain the theory of the preparation of magnesic carbonate 
from Dolomite. 

11. The symbol of magnesic sulphate may be written MgSO v 
or Mg=O a =SO a , or Mgo=SO % . What different ideas do these forms 

suggest ? 

12. Write the reaction of sulphuric acid on the two constituents 
of dolomite, and show how pure Epsom salt may be thus prepared. 

13. Write the reaction of a solution of gypsum on magnesic 
carbonate. 

14. Represent by graphic symbols MgSO^ . H/). 

15. Represent by graphic symbols the composition of potassic 
magnesic sulphate, and explain the relations of the crystallized salt 
to Epsom salt. 

16. Write the reaction of hydrochloric acid on magnesic carbonate. 

17. Explain the decomposition which results when a solution of 
magnesic chloride is evaporated in the air, and why an atmosphere 
of II CI should prevent the change. 

18. What is the difference ^between the relations of baric and 
magnesic carbonate to calcic carbonate? 

Ans. The first is related to Aragonite, the second to Calcite. 

19. What is the difference between the reactions of sodic carbon- 



QUESTIONS AND PKOBLEMS. 361 

ate on solutions of calcic and magnesic salts, and on what does the 
difference depend ? Write the reactions in the two cases. 

20. What is the difference between the reaction of amnionic car- 
bonate on the same solutions ? 

21. Write the reaction of sodic phosphate on a solution of mag- 
nesic and amnionic chloride. 

Ans. (MgCl 2 + NH 3 -f H,Na,=O^PO + Aq) = 

(jm 4 ),]JIsK> 3 =FO . GH 2 G -|- (2NaCl -f- Aq.) 

22. Write the reactions when zinc blende and smithsonite are 
calcined. 

Ans. ZnCO z = ZnO -j- C0 2 , and 2ZnS -j- 3®=® = 

2ZnO -f- 2S0 2 . 

23. Write the reaction when zincic oxide is reduced. 

Ans. ZnO -j- C = Sn + O®. 

24. Write the reactions of dilute sulphuric, hydrochloric, and 
acetic acids on zinc. 

25. What part does zinc play in reaction [330] ? 

26. In what different ways may the symbol of zincic hydrate be 
written ? Ans. Zn=0= 2 H 2 , Zn=Ho 2 , Zno=H r 

27. When zincic hydrate dissolves in caustic soda, what is formed ? 

28. Write the reaction of sodic carbonate upon a solution of zincic 
sulphate, assuming that three molecules of zincic hydrate are formed 
to every two molecules of zincic carbonate. 

Ans. (5ZnS0 4 -f bNa o C0 3 -4- 3H 2 -f Aq) = 

2ZnC0 3 -f- 3ZnHo 2 -f- ( < 5Na 2 SO i -j- Aq) + 3@® 2 . 

29. In what different ways may the symbol of zincic sulphate be 
written, both the anhydrous salt and the salt with one molecule of 
water? Represent graphically. 

30. Write the symbol of potassic zincic sulphate. What is the 
crystalline form of this double salt, and with how many molecules of 
water does it crystallize? 

31. Write the reaction of ammonic sulphide on a solution of zincic 
sulphate. 

Ans. (ZnSO, -f (NH^S -f Aq) = 

Z11S + ((NTQ 2 SO, + Aq). 

32. Write the reaction of sulphuretted hydrogen on a solution of 
zincic acetate. 

33. Would zincic sulphide be precipitated from a solution of zincic 
chloride containing an excess of hydrochloric acid? What is the 
difference between this case and that of 32 ? (21.) 

16 



362 QUESTIONS AND PROBLEMS. 

Cadmium. 

34. Write the reaction of dilute sulphuric acid on cadmium. 

35. Write the reaction of sodic hydrate on solution of cadmic 
sulphate. 

36. Write the reaction of zinc on solution of indium chloride. 

37. Write the reaction of sulphuretted hydrogen on solution of 
cadmic chloride. 

38. By what reactions may cadmium be separated from zinc ? 
Ans. By metallic zinc, by ammonic carbonate, and by sulphuret- 
ted hydrogen. 

39. What is the electrical order of magnesium, zinc, indium, and 
cadmium ? 

40. Assuming that the atomic weight of cadmium is 112, what in- 
ference may be drawn 'from the Sp. Gr. of its vapor in regard to the 
constitution of its molecule ? Does the conclusion have any bearing 
on the other dyad elements ? 



§ 328.] GLUCINUM. — YTTEIUM. — ERBIUM. 363 



Divisions VIII. and IX. 

327. GLUCINUM. Gl = 9.3. — Dyad. A metallic ele- 
ment, found only in the Beryl, Glo 3 ={Si' 6 6 )=Al^>, the Chryso- 
beryl, Glo=Al 2 2 , and a few other rare minerals. The metal is 
very light, Sp. Gr. 2.1, is malleable, has a bright white lustre, 
does not alter in the air even when heated, and does not decom- 
pose aqueous vapor at a red heat. It resembles aluminum, as 
do also its oxide, hydrate, and chloride the corresponding com- 
pounds of the same metal. The hydrate differs, however, from 
that of aluminum in several important respects. Although sol- 
uble in caustic alkalies, it is again precipitated on boiling the 
diluted solution. It dissolves in solutions of carbonate of am- 
monia, with which it forms a crystalline salt. It yields with 
sulphuric acid a well-crystallized sulphate, GlS0 4 . 4II 2 0, which 
forms with potassic sulphate a double salt, K 2 ,Gl=(SO i ) 2 . 2H 2 O f 
wholly different from alum. Lastly, it absorbs C0. 2 from the 
air. The salts of this metal have an acid reaction and a sweet 
taste, whence the name from yXvKvs. 

328. YTTRIUM, r=61.7, and ERBIUM, ^= 112.6. 
1 — Dyads. Metallic elements associated together in Gadolinite, 
Yttrotantalite, and a few other very rare minerals. First rec- 
ognized in the specimens from Ytterby, in Sweden, whence the 
names. In most of their relations they quite closely resemble 
glucinum. They differ, however, from it in forming insoluble 
oxalates, and hence are precipitated on adding an excess of ox- 
alic acid to solutions of their salts. Their hydrates also are in- 
soluble in caustic soda or potash, although they dissolve readily 
in solutions of ammonia and its carbonate. The oxide of yttrium 
is white, that of erbium slightly rose-colored. Oxide of er- 
bium, when heated in a colorless flame, shines with a green li^ht, 
although it does not volatilize ; and with the spectroscope the 
unique phenomenon is seen of brilliant colored bands superim- 
posed on a continuous spectrum. Moreover, solutions of erbium 
salts absorb the same colored rays which the ignited oxide 
emits; and when a luminous flame is viewed with a spectro- 
scope through such a solution, dark bands are seen which have 
the same position a-^ the luminous bands just mentioned. The 
salts of yttrium exhibit no phenomena of this kind. 



364 QUESTIONS AND PROBLEMS. [§329. 

329. CERIUM. Ce = 92. LANTHANUM. Za = 93.6. 
DIDYMIUM. D = 95. — These three rare elements are found 
inseparably united in Cerite, Allanite, Lanthanite, Yttrocerite, 
Parisite, and several other very rare minerals. They are not 
unf'requently associated with the elements of the last section, 
which they resemble in many particulars, but they differ from 
them in forming with potassium insoluble double sulphates, and 
hence they are precipitated on adding an excess of potassic sul- 
phate to solutions of their salts. They all yield oxides of the 
form RO, but cerium differs from the other two in forming a 
higher oxide, probably Cr z O±, which, when heated with hydro- 
chloric acid, evolves chlorine. The oxides of cerium and lan- 
thanum are more or less colored, and that of didymium is dark 
brown. The salts of didymium are pink or violet colored, and 
when in solution, even in small quantities, absorb powerfully 
certain rays of light; and the spectrum of a luminous flame 
viewed through such a solution shows a strong absorption band 
in the yellow and another in the green. As these bands differ 
wholly from those of erbium, they enable us to recognize with 
certainty the presence of didymium, as none of its associated 
elements produce any such effect. Moreover, since the char- 
acteristic absorption bands are seen with reflected as well as 
with transmitted light, we are enabled to extend this mode of 
investigation even to opaque solids. 

In regard to the elementary substances but little is known. 
Cerium, which has been obtained by reducing its chloride with 
sodium, is a soft metal like lead. When polished, it exhibits a 
high metallic lustre, and its specific gravity is about o.o. 

Questions and Problems. 

1. Some chemists regard glucina as a sesquioxide, like alumina, 
and hence write the symbol Gl 2 O r What would then be the atomic 
weight of jjucinum ? Ans. 14. 

2. By what two reagents may the elements of this section be di- 
vided into three groups? Ans. Oxalic acid and potassic sulphate. 

3. When mixed with the other allied oxides, the amount of eerie 
oxide present may be determined by dissolving out of contact with 
the air a weighed amount of the mixed oxides in hydrochloric acid, 
to which some potassic iodide has been added, and then finding by 
[272] the quantity of iodine thus set free. Write the reactions illus- 
trating the theory of the process. 

Ans. in part. Ce 3 4 + 8HCI = SCeCl 2 -f- 4H 2 -\-Cl~CL 



§330.] 



NICKEL. 



365 



Division X. 

330. NICKEL. Ni = 58.8. — Quantivalence usually two. 
One of the less abundant metallic elements. The chief native 
compounds are 



Breithauptite 


Hexagonal 


Mi[Sb 2 l 


Kupfer nickel 


Hexagonal 


NiilAs^ 


Chloanthite (Niccoliferous 




Smaltine) 


Isometric 


Ni=[_As 2 ~], 


Nickel Glance 


Isometric 


m^s 2 [As 2 -]i 


Rammelsbergite 


Orthorhombic Ni=\_As 2 ~\, 


Millerite 


Hexagonal 


MS, 


Bunsenite 


Isometric 


NirO, 


Nickel Vitriol 


Monoclinic 


Ni=0 2 =S0 2 .lff 2 0, 


Annabergite (Ni 


ckel 




green) 


Monoclinic 


M A WS(AsO) 2 ,$ir 2 0, 


Emerald Nickel 


(Zaratite) 


m 3 W 6 iCO,H 4 .iE 2 0, 


Genthite 




[M,l¥ff] 4 ym0 8 VmSl 3 2 . QIT 2 0. 



The metal, however, is obtained chiefly from a niccoliferous 
iron pyrites (magnetic variety), which only contains the element 
as an accessory constituent. The native arsenides, and an im- 
pure regulus (called speiss) formed in the preparation of smalt, 
are the other sources of the nickel of commerce. The process 
of extracting the metal is complicated and tedious. It consists 
in roasting the ore, dissolving the resulting oxides in acid, and 
precipitating first the associated metals, and afterwards the 
nickel, by appropriate reagents. The chief difficulty is to sep- 
arate from the nickel the more valuable cobalt, with which 
nickel is almost invariably associated, and to which it is very 
closely allied. 

Metallic nickel, Sp. Gr. 8.82, has a silver-white color, a bril- 
liant metallic lustre, and does not tarnish when exposed to the 
atmosphere. It has great tenacity and malleability, and, were 
it more abundant, would rival even iron in the number of its 
applications in the useful arts. Nickel resembles iron in many 
of its qualities. When pure, it is nearly as infusible as wrought- 



366 NICKEL. [§ 330. 

iron, and may be forged in a similar way. When combined 
with a small amount of carbon, it may, like cast-iron, be fused 
in an ordinary wind furnace. Nickel is also, like iron, suscep- 
tible of magnetism, but the magnetic power is less marked, and, 
when heated, it loses this virtue at a much lower temperature. 
Moreover, like iron, nickel is soluble in dilute sulphuric or 
hydrochloric acids with evolution of hydrogen gas, but the ac- 
tion is less energetic, and the metal dissolves only slowly. The 
best solvents are nitric acid and aqua ivgia. Nickel forms with 
copper a brilliant white, hard, tenacious, malleable alloy, and 
a small amount of nickel will whiten a large body of copper. 
This alloy is much used for coinage, and as the ba.^is of the 
better kinds of electrotype plate. German silver is an alloy of 
copper, zinc, and nickel in about the proportion of 5:3:2. 
Nickel may also be alloyed with iron, and is a constant constit- 
uent of the metallic meteorites. Nickel readily combines with 
each of the members of the chlorine group of elements, but 
only in one proportion, and the compounds thus formed, NiF 2 , 
NiCl 2 < &c, are all soluble in water. 

There are two oxides of nickel. The protoxide, NiO, is an 
olive-green powder, readily obtained by igniting either the ni- 
trate or the carbonate of the metal. It is a ba.-ic anhydride, 
dissolving readily in the mineral acids, and forming the ordinary 
nickel salts, in all of which Ni acts as a bivalent radical. The 
sesquioxide, Ni 2 3 , is a black powder, also obtained by igniting 
the nitrate, but at a lower temperature. It is an unstable com- 
pound, and, when heated, is resolved into the lower oxide and 
oxygen gas. It is not a basic anhydride, and, when heated with 
the mineral acids, one third of the oxygen is given off as before, 
and a salt of the ordinary type is the result. In the sesquiox- 
ide, Ni is a quadrivalent, but the double atom (Ni 2 ) acts as a 
sexivalent radical. The tendency to form radicals of this last 
type, which is only foreshadowed in nickel, becomes a striking 
character in the elements which follow in our classification. 

Of the crystallized soluble salts of nickel, the most common 
are 

Niccolous Chloride Ni Cl 2 .9R 2 0, 

Niccolous Nitrate Ni=0 2 =(N0 2 ) 2 . §H 2 0, 

Niccolous Sulphate Ni.H 2 =OfSO . QJI 2 0, 

Dipotassic-niccolous Sulphate Ni,K 2 =Of(S0 2 ) 2 .§H 2 0. 



§331.] COBALT. 367 

The salts of nickel, both when crystallized and when in so- 
lution, have a characteristic green color ; but, when rendered 
anhydrous by heat, this color changes to yellow. From their 
solutions the fixed alkalies precipitate a hydrate, and the alka- 
line carbonates a basic carbonate, of nickel, both iorming pale- 
green precipitates. The first is probably the definite compound 
Ni=0 2 =H 2 ; but the composition of the second varies with the 
temperature, strength, and proportions of the solutions em- 
ployed, and the product is closely analogous to the precipitates, 
which are obtained under similar conditions from solutions of 
the salts of magnesium or zinc. 

The salts of nickel readily combine both with ammonia and 
with the ammonium salts. A large number of products may 
thus be formed, which are easily soluble in water. The fol- 
lowing crystalline compounds, which indirectly play an impor- 
tant part in some of the methods of qualitative analysis, will 
serve as types of the class : — 

Ni Cl 2 . 6JW55, NH< CI . M Cl 2 . <oH 2 0. 

From solutions of such ammoniacal compounds, and from 
other alkaline solutions containing nickel, the metal is precipi- 
tated as [M 2 ]%OqIHq, both by chlorine gas and by the alkaline 
hypochlorites. The precipitate has an intense black color, and 
this reaction is one of the most delicate tests for nickel, but 
does not distinguish it from cobalt. Nickel is also precipitated 
from alkaline solutions by JI 2 S or by alkaline sulphides. The 
black precipitate thus obtained has the same composition as 
Millerite, NiS. It is insoluble in the dilute mineral acids, al- 
though in acid solutions of nickel salts H 2 S gives no precipitate. 
Two other sulphides of the element, Ni 2 S and NLS 2 , have been 
described. 

331. COBALT. Co = 58.8. — Quantivalence usually two. 
Associated with nickel in the same ores, but less abundantly 
distributed. Most of the minerals enumerated in the last sec- 
tion contain cobalt. When, however, this metal preponderates, 
they are in most cases classed as separate mineral species, and 
receive distinct names. No cobalt mineral corresponding to 
Kupfernickel or Breithauptite has been found, but we have 



368 


COBALT. 


[§< 


Smaltine 


Isometric 


Coi[A 2 ], 


Cobaltine 


Isometric 


Coi[S 2 ,(As 2 )*], 


Linugeite 


Isometric 


Co 3 S 4 , 


Glaucodot 


Orthorhombic Co=[S 2 ,(As 2 )2, 


Syepoorite 




Co=S, 


Cobalt Vitriol 


Monoclinic 


Co=OfSo 2 .7ir 2 o, 



Ery thrite ( Cobalt Bloom) Monoclinic Co 3 l 6 l(As 0) 2 . SII 2 0. 

To these must be added an impure oxide of cobalt (Earthy 
Cobalt), and a miueral called Remingtonite, which probably 
corresponds to Emerald Nickel. There is a variety of Lin- 
nseite, called Siegenite, which contains a large proportion of 
nickel; but no purely niccoliferous compound of this type is 
known. 

In all their chemical relations, the two metals here associ- 
ated resemble each other so closely that the description of 
nickel given above applies almost word for word to cobalt, and 
it is only necessary to indicate farther the points of difference. 

Metallic cobalt rusts more readily than nickel, but less read- 
ily than iron. It is magnetic, and possesses valuable qualities, 
but is so costly that it has received no application in the arts. 

Cobalt forms but one stable compound with either of the mem- 
bers of the chlorine group of elements, CoOl 2 , &c. ; but by dis- 
solving Co 2 O s in hydrochloric acid a red solution is obtained, 
which is supposed to contain Co 2 Cl 6 . The compound, however, 
is very unstable, for the solution evolves chlorine on the slight- 
est elevation of temperature. 

There are three well-marked oxides of cobalt. Cobaltous 
Oxide, CoO; Cobaltic Oxide, Co 2 3 ; Cobaltous-cobaltic Ox- 
ide, Co 3 4 ; but, besides these, several others have been dis- 
tinguished, which are probably either mixtures or molecular 
aggregates of the first two. Not only is Co a strong basic 
anhydride, like NiO, but also Co 2 3 dissolves in acids, espe- 
cially in acetic acid, forming salts. We have, therefore, to dis- 
tinguish between cobaltous and cobaltic salts ; but the last are 
very unstable and little known. 

The ordinary cobaltous salts, when crystallized, are red, but 
are usually lilac-colored when anhydrous, and the pink solu- 
tions, which they yield with water, become blue when concen- 
trated. On this change of color depends the virtue of certain 



§331.] COBALT. 369 

sympathetic inks. From solutions of these salts, potassic or 
sodic hydrate precipitate Co = 2 =H 2 ' l which has a delicate rose- 
color. The pale-blue precipitate, which generally falls first, is 
a basic salt of cobalt, but if warmed with an excess of the re- 
agent, it soon acquires the composition and color of the normal 
hydrate. If exposed to the air this hydrate absorbs oxygen 
rapidly, and changes to a dingy-green color. The normal co- 
baltic hydrate is not known. The black precipitate obtained 
by the action of chlorine or the hypochlorites on alkaline solu- 
tions containing cobalt is the second anhydride of this hydrate, 
or Of[_ Co 2 ~] = O.fH.^ The same compound is formed when chlo- 
rine gas is passed through water or a solution of caustic potash 
holding cobaltous hydrate in suspension. When the alkali is 
used, the whole of the hydrate is converted into the cobaltic 
compound ; but with pure water only two thirds as much are 
obtained. The compound of nickel formed under the same 
conditions is supposed to be the normal niccolic hydrate. 

The tendency to form soluble compounds with ammonia and 
with the ammonium salts manifested by nickel, appears again 
and more prominently in the allied element cobalt. Moreover, 
there are cobaltic as well as cobaltous compounds of this class, 
and the last tend to pass into the first by absorbing oxygen 
when exposed to the air. The number of these compounds is 
very numerous. They have a very complex constitution, and 
in many cases at least are probably formed on the ammonia 
type. We may reirard them as compounds of ammonio-cobalt 
bases, to several of which distinctive names have been given. 
The following scheme exhibits the relations of the more impor- 
tant compounds : — 

Cobaltous Compounds. 
CoR . ANff 3i CoR . %NH» 

Cobaltic Compounds. 

n 
[ Co 2 j R s . SNH S Fusco-cobaltic salts. 

ii 
[Co 2 ~\R z . \0NHs Roseo or Purpureo-cobaltic salts. 

ii 
[Cb 2 ]i?3 . \2NH Z Luteo-cobaltic salts. 

ii 
In the above symbols R stands for a bivalent acid radical, 
16* x 



370 COBALT. [§331. 

like (S0 4 ), (CO '„), (Q0 4 ) or Cl 2 , (!TO a )» &c. Substituting 
these in the general symbol, we obtain the specific symbols of 
the various salts of the a.-sumed bases ; but in most cases the 
cry.-tallized salt contains in addition one or more molecules of 
water, which frequently play an important part in its constitu- 
tion, and determine marked differences of qualities, as in the 
following typical compounds: — 

Purpureo-cobaltic Chloride [(7o 2 ]C7 6 . 10NH Z , 
Roseo-cobaltic Chloride [ Co 2 ] CI 6 . 10 NJI 3 . 2H 2 0, 

Xantho-cobaltic Chloride [ Co 2 ] Cl 6 . 10NB 3 . JV 2 2 . H 2 0. 

Cobaltous oxide combines with many of the basic as well as 
with the acid anhydrides, yielding in several cases compounds 
distinguished by great brilliancy of coloring. The compound 
with \_Ah~] 3 is known as Thenard's blue, that with ZnO as 
Rinman's green. Such compounds are formed when the me- 
tallic oxides, moistened with a solution of cobaltous nitrate, are 
heated before the blow-pipe, and the production of the color is 
one of the most characteristic blow-pipe reactions. 

Cobaltous oxide, when melted into glass or into the glaze of 
earthenware, imparts to the material an intense blue color, and 
the brilliancy and the depth of the color render the oxide one 
of the most valuable verifiable pigments, and this is its chief 
use in the arts. The blue pigment called smalt, used for color- 
ing paper and dressing white calicoes, is a pulverized alkaline 
glass strongly colored with the oxide. 

Cobalt is distinguished by the same reactions as nickel from 
all other metallic radicals. From nickel it is distinguished, — 
First, by the blue color which the oxide gives to borax glass. 
Secondly, by the fact that potassic nitrite precipitates 1 the co- 
balt from nitric or acetic acid solutions, while it does not precip- 
itate nickel. Thirdly, by the circumstance that cyanide of co- 
balt forms, when boiled with a solution of potassic cyanide in 
contact with the air, a compound corresponding to potassic ferri- 
cyanide. The solution of potassic cobalti-cyanide is not de- 
composed by HgO or by alkaline hypochlorites, while from the 
solution of the cyanide of nickel and potassium, formed under 

1 Composition of precipitate according to S. P. Sadtler, 
#6> [Co 2 ]xii0 12 xii(iV 2 2 ), ; . xH.,0. 



331.] 



QUESTIONS AND PROBLEMS. 



371 



the same circumstances, all the nickel is precipitated by the 
same reagents. 

CaG+(2H-GJ^+Aq)=zCo'(€K) i +(B i O+Aq.) [333] 

4Co=(CJW) 2 + (12K-CN+ 4H-GW+ Aq)+©=© = 

{2K,l{C l2 N 12 Oo 2 ) + 2H 2 + Aq). [334] 

Ni© + (4iT-CiV+ H 2 + Aq) = 

(2K- ON. m-( CN) 2 + 2K-OH-\- Aq), [335] 

Mg© + (2K-CN. Ni-(CN) 2 + B 2 -f Aq) = 

Ri-OfH, + {2K-CN. By=(CN) 2 + ^). [336] 



Questions and Problems. 

1. Represent by graphic symbols the constitution of Kupfernickel 
and Chloanthite. 

2. In the symbol of Nickel Glance, in what relation does the sul- 
phur stand to the arsenic ? Could these elements replace each other 
by single atoms ? 

3. What is the distinction between Chloanthite and Rammels- 
bergite? Does the same distinction reappear in the corresponding 
compound of either of the allied elements ? 

4. Have any facts been stated which prove that nickel is some- 
times quadrivalent? 

5. Represent by a graphic symbol the constitution of niccolous 
sulphate. 

6. Write the reaction of sulphuric acid, and also of hydrochloric 
acid, on Ni 2 O s . 

7. Point out the analogies between nickel and zinc. 

8. Thp precipitate first formed by ammonia or amnionic carbon- 
ate in solutions of the salts of nickel redissolves in an excess of the 
reagent, and does not form at all when a large amount of amnionic 
chloride is present. How do you explain these reactions ? 

9. In the native compounds of cobalt this element is more or less 
replaced by iron and nickel. Write the symbols of Smaltine and 
Cobaltine so as to indicate this fact. 



372 QUESTIONS AND PROBLEMS. 

10. Represent by graphic symbols the constitution of Linnaeite, 
and also that of Co 2 S 3 and CoS 2 , the only other sulphides not men- 
tioned in the text. 

11. Represent by graphic symbols the constitution of the follow- 
ing oxides and oxy sulphides, Co 3 O t , Co 6 O p Co s OS. 

12. In what respects do the oxides and sulphides of cobalt differ 
from those of nickel ? 

13. Write the reaction of chlorine gas on cobaltous hydrate, first, 
■when suspended in water, and, secondly, when suspended in solution 
of caustic potash. Write also the corresponding reactions which 
take place when hydrate of nickel is similarly treated. 

14. Represent the composition of the ammonio-cobalt salts by 
typical symbols. 

15. In potassic cobalti-cyanide what is the quantivalence of co- 
balt? Do the cobalt atoms change their atomicity in [334] ? 

16. Analyze reactions [333] to [336], and show that the differ- 
ences in the relations of cobalt and nickel to the alkaline cyanides 
depend on differences in the atomic relations of the two elements. 
What part does the oxygen of the* air play in [334]? 

1 7. Potassic cobalti-cyanide is formed when cobaltous hydrate is 
boiled with a solution of potassic cyanide, there being free access of 
air. Write the reaction. 

18. Write the reaction when a solution of potassic hypochlorite 
(K-O-Cl) is added to the product of reaction [335]. 

19. Point out the resemblances and the differences in the chemi- 
cal relations of cobalt and nickel, and show how far they may be 
traced to the circumstance that the radical [CoJ is more stable than 
the radical [iV7J. 



§332.] MANGANESE. 373 



Division XL 

332. MANGANESE. Mn = 55. — Quantivalence two, 
four, six, and possibly eight. A tolerably abundant element, 
and widely diffused throughout the mineral kingdom, entering 
into the composition of a very large number of minerals. The 
following are the most characteristic or important: — 

Pyrolusite Orthorhombic Mn0 2 , 

Braunite Tetragonal Mn 2 3 or (MnSi)l0 3 > 

Hausmannite Tetragonal Mn 3 4 , 

Psilomelane Massive ) Mixtures of different 

Wad Earthy ) oxides, 

Manganite Orthorhombic Of[Mn 2 '] = 2 =II 2i 

Hauerite Isometric MnS 2 , 

Manganblende Isometric MrnS, 

Rhodonite Triclinic Mn=0 2 =SiO, 

Tephroite Orthorhombic Mn^OfSi, 

Triplite Orthorhombic ([Fe,Mn] 2 -F)^Of(PO)? 

Manganese Spar Rhombohedral Mn = 2 =CO, 

Mangano-calcite Orthorhombic [C«,J//a]=0 2 = (70. 

The elementary substance is a very hard and brittle metal, Sp. 
Gr. 8.013. It has a grayish-white color, is almost infusible, 
and very slightly magnetic. It oxidizes rapidly in moist air, 
and decomposes water even at the ordinary temperature. 
There appear to be two conditions of the metal corresponding 
to wrought and cast iron ; but its properties have not been 
thoroughly studied. It is obtained with difficulty by reducing 
the oxide with carbon at a very high temperature, and as yet 
has found no applications in the arts. Corresponding to the 
three degrees of quantivalence of Manganese are three classes 
of compounds. 

1. Manganous compounds, in which the quantivalence of the 
element is two. This class includes all the manganese minerals 
above enumerated, after manganblende, and all the common 
soluble salts of the metal. Among the last the most important 
are 



374 MANGANESE. [§ 332. 

Manganous Chloride MnCl 2 . (2 or 4i7 2 0), 

Manganous Sulphate Mn = 0.fS0 2 . (4, 5, or 7ff 2 0) t 

Dipotassic-manganous Sulphate K 2 ,3I/i^O i =\_S0 2 ] 2 • §H 2 0. 

There is also a Bromide, MnBr 2 . 2H 2 0. The manganous 
compounds are distinguished by a delicate pink or red color. 
From solutions of the manganous salts, potassic or'sodic hy- 
drate precipitate a white hydrate, Mn=0.fH 2 , which absorbs 
oxygen rapidly, and becomes brown when exposed to the air 
(Manganese Brown). In like manner sodic or potassic car- 
bonate precipitate a white hydro-carbonate, which also becomes 
brown on drying. Amnionic carbonate also produces the same 
precipitate, and does not redissolve it when added in excess. 
Amnionic hydrate, on the other hand, gives no precipitate in 
solutions containing an excess of amnionic chloride, and redis- 
solves the precipitate which first forms in simple aqueous solu- 
tions. Ammonio-manganous salts are thus formed, and two 
well-crystallized ammonio-manganous chlorides have been de- 
scribed, MnC! 2 .2NH 4 Cl . H 2 and MnCl 2 . NHjCl . 2H 2 0. 

In the solution of a manganous salt, sodic phosphate and am- 
monia produce, under regulated conditions, a highly crystalline 
precipitate having the composition (NH A ) 2 .Mn 2 lO^(PO) 2 • 
2H 2 0. This precipitate yields on ignition a pyrophosphate of 
uniform composition, and on this reaction is based a valuable 
means of determining the amount of manganese in quantitative 
chemical analysis. 

Manganous oxide, MnO, is easily obtained by reducing either 
of the higher oxides with hydrogen. It is an olive-green pow- 
der, which burns if heated in the air, thus forming the k ' red 
oxide" Mn 3 4 . 

Manganous sulphide is precipitated on adding an alkaline 
sulphide to the solution of a manganous salt, as a flesh-col- 
ored hydrate, MnS . xH 2 ; but this also in contact with the 
air rapidly oxidizes and turns brown. It readily dissolves in 
the dilute mineral acids, and also in acetic acid. The same 
tendency to form compounds, in which manganese presents a 
higher order of quantivalence, is exhibited by all the soluble 
manganous salts, and especially by the ammoniaeal solutions just 
mentioned, which, when exposed to the air, rapidly absorb oxy- 
gen, become turbid, and deposit a brownish flocculent precipitate 



§332.] MANGANESE. 375 

of manganic hydrate (O^Mn^HfOJ). So, also, when chlo- 
rine gas is passed through water holding manganous hydrate or 
carbonate in su pension, or through a solution of a manganous 
salt, to which an excess of sodic acetate has been added, the 
manganese is still further oxidized, and the brownish precipitate 
obtained is chiefly a hydrate of the dioxide Mn 2 . H 2 0. Bro- 
mine also produces a similar result. 

2. Manganic compounds, in which the quantivalence of the 
element is four. Of these we must distinguish two divisions: 
first, those which have for their radical the single quadrivaleut 
atom of manganese; second, those in which two such quadriva- 
lent atoms act as a compound radical with a quantivalence of 
six. To the first division of the manganic compounds probably 
belong most of the native oxides. Pyrolusite, Mn0 2 , has a 
crystalline form similar to that of Brookite, Ti0 2 , which is 
an oxide of the well-marked tetrad element titanium; while 
Braunite, Mn 2 3 , and Hau-mannite, 3Tn 3 4 , have a form which 
is nearly isomorphous with Rutile, an allotropic state of the 
same oxide (Fig. 37), but wholly unlike the forms of Fe 2 O s 
(Fig. 44) and Fe 3 4 (Fig. 33), two typical compounds, to 
which Braunite and Hausmannite, if containing the sexivalent 
radical \_Mn 2 \ must be closely allied. Manganite probably 
contains tiis radical, as it is isomorphous with the native ferric 
hydrate, Gothite. 

Of the oxides of manganese, the red oxide, Mn 3 4 , is the 
most stable. The higher oxides, when heated, are all resolved 
into Mn 3 4 , and the native oxides thus become sources of oxy- 
gen gas [232]. When heated with sulphuric and, they also 
give off oxygen and yield manganous sulphate [231]. When 
heated with hydrochloric acid, they liberate chlorine and yield 
manganous chloride [77]. Hence an important application of 
the native oxides in the arts. There are reasons for believing 
that the two atoms of oxygen in Mn0 2 stand in different rela- 
tions to this molecular group (236), and the chloride of man- 
ganese, 3InCI 4 , recently isolated, affords still more conclusive 
evidence of the quadrivalent relations of this element. This 
manganic chloride is exceedingly unstable, and when gently 
heated breaks up into manganous chloride and chlorine gas. 

To the second division of the manganic compounds belong 
manganic hydrate, OfiJdn^OfH^ and several very unstable 



376 MANGANESE. [§ 332. 

compounds, which have been formed by dissolving this hydrate 
in different acids. The sulphate, however, becomes stable when 
the hexad radical is associated in the salt with potassium. We 
thus obtain an interesting variety of alum, 

K 2 lMn 2 ']^O s y^lS0 2 ] i . 2±H 2 0. 

3. The most characteristic compounds of manganese are 
those in which the element is either sexivalent or octivalent, 
and the fact that a volatile fluoride of manganese is known, 
which contains at least six atoms of fluorine to every atom of 
manganese, indicates that the atomicity of the elements cannot 
be less than six. Indeed, the fluorides illustrate \^ry strikingly 
the different degrees of quantivalence which manganese may 
assume, for we have MnF 2 , MnF 4 , \_Mn 2 ~]F^ and MnF 6 . 

When an intimate mixture of K-0-Ha,n<\3fn0 2 is roasted in 
a current of oxygen gas, the following reaction takes place : — 

4K O H + 21n0 2 + ®=® = 

2M 2 =© 2 =iTIift© 2 + 2m 2 0. [337] 

On dissolving the resulting mass in water, and evaporating the 
deep green solution thus obtained (in vacuo), crystals are formed 
isomorphous with K 2 =0.fS0 2 , in which the hexad atoms of man- 
ganese act as acid radicals, and we call the product potassic 
manganate. The acid corresponding to this compound has never 
been isolated, and only a few of its salts are known. They are 
all, like potassic manganate, exceedingly unstable. 

On boiling a solution of potassic manganate, the following 
remarkable reaction results : — 

(SK 2 =0 2 =Mn0 2 -\-3H 2 + Aq) — 

Mn0 2 . M 2 + {K 2 -0 2 \Mn^ 0,+ 4K-0-H+ Aq) ; [338] 

and a new compound called potassic permanganate is formed, in 
which the atoms of manganese appear to have a quantivalence 
of eight. The reaction takes place more readily if a stream of 
C0 2 is passed through the boiling solution to neutralize the 
K-O-Has it forms, and when the solution is not too strong the 
carbonic anhydride of the atmosphere will in time determine the 
same change even at the ordinary temperature. The solution 
of K i =OfMn 2 & has a deep violet color, and the changing tints, 



§333.] IRON. 377 

during the reaction just described, present a very striking phe- 
nomenon. Hence the crude potassic manganate, obtained by 
melting together M>i0 2 and K- 0~N0 2 , is commonly known as 
chameleon mineral ; and the production of the characteristic 
green color, under similar conditions in a blow-pipe bead, is the 
best evidence of the presence of manganese. 

Potassic permanganate, prepared as above, may be readily 
crystallized, and its crystals are i-omorphous with those of po- 
tassic perchlorate ; that is, Kf Of[Mn 2 ~] *u 6 has the same form 
as K-0-Cl=0 3 . From potassic permanganate a number of other 
permanganates may be prepared, and also permanganic acid, a 
dark-colored volatile liquid. Permanganic acid is formed when 
the solution of a manganese salt is boiled with nitric acid and 
plumbic dioxide, and a violet color developed in the liquid under 
these conditions is a certain indication of the presence of man- 
ganese. The permanganates are more stable than the manga- 
nates, but still they readily part with a portion of their oxygen, 
and act as powerful oxidizing agents. A solution of potassic 
permanganate is much used for this purpose in the laboratory. 
For example, it changes ferrous into ferric salts. 

(10Fe-O z =SO a + K 2 =Of[Mn 2 -}0, + SM,=0 2 =S0 2 +Aq) = 

(5[F,JlOJ[^0J 3 + ^0 2 =S0 2 +2J^^ 2 ^0 2 + 8// 2 0-}-Jg).[339] 

The slightest excess of the permanganate is at once indicated by 
the color it imparts to the liquid, and the reaction is the basis 
of one of the most valuable methods of volumetric analysis. 
Both the manganates and the permanganates are at once de- 
composed by all organic tissues, which they rapidly oxidize, 
and a crude sodic permanganate is much u.-ed as a disinfecting 
agent. 

333. IRON. Fe = 56.— Usually bivalent or quadrivalent, 
but rarely sexivalent. A universally diffused element, and 
the most abundant and important of the useful metals. As an 
accessory ingredient, it enters into the composition of almost 
every substance, and it is the chief metallic radical of a very 
large number of important minerals. 



378 



IRON. 



[§333. 



Oxides. 



MAGNETITE 


Isometric 


Fe\Fe 2 ~\ viu0 4 , 


Magnesioferrite 


Isometric 


MglFe^vmOt, 


FRANKLINITE 


Isometric 


[Z^Mll^Fe^vmO* 


HEMATITE 




[*yift, 


Specular Iron 


Hexagonal, 




Red Hematite 


Massive, 




Clay Iron Stone 


Massive, 




Red Ochre 


Massive, 




MENACCANITE 




(Ti-Fe)W 3 , 


Titanic Iron 


Hexagonal. 
Hydrates. 




Limnite 


Massive 


[FeJWm, 


Xanthosiderite 


Massive 


0=[Fe 2 ]W^/f 4 , 


Gothite 


Orthorhombic 


O^Fe^O^ 


LIMONITE 




O^Fe^O^H^ 


Brown Hematite 


Massive, 




Brown Clay Iron 






Stone 


Massive, 




Bog Ore 


Massive, 




Yellow Ochre 


Massive. 
Carbonates. 




SIDERITE 




Fe-0 2 =00, 


Spathic Iron 


Rhombohedral, 




Clay Ikon Stoxe 






(of the coal-beds) 


Massive, 




Sph^erosiderite 


Concretionary, 




Mesitite 


Rhombohedral 


[Mg.FeyO.fCO, 


Ankerite 


Rhombohedral 
Sulphides. 


[M^Fe^CaW+^CO)? 


Troilite 


Massive 


FeS, 


Magnetic Pyrites 


Hexagonal 


Fe 7 S s or Fe 2 S 2 ? 


Iron Pyrites 


Isometric 


FeS 2 , 


Marcasite 


Orthorhombic 


FeS 2 , 


Mispickel 


Orthorhombic 


M*CAE- 



§334.] 



IRON. 



379 



Sulphates, 
Green Vitriol Monoclinic H 2 Fe=OfSO . 6R 2 O f 

Pisanite Monoclinic R^Fe.Cu^O^SO . G# 2 0, 

Coquimbite Hexagonal [Fe 2 ]W b i[S0. 2 ] 3 .9II 2 0j 

Jaroaite Rhombohedral 

^(o^lFe.y-o^so,) . (iK,jsrcq=o<fS0 2 ) . §h 2 o, 

Copiapite Hexagonal? O=[i^ 2 ] 2 xO 10 x[£O 2 ' 5 . UH 2 0, 

Raimondite Hexagonal 3 I[J^ 2 ] 2 IOJ[/S'0 2 J 3 . 7 H 2 0, 

Giockerite Massive & x[Fe 2 \=0fSO 2 . 0>H 2 O, 

Fibroferrite Fibrous O 4 viii[^e 2 ] 3 x(9 10 x[^O 2 ] 5 . 27 R 2 0, 

Botryogen Monoclinic 

O 4 vin[i^ 2 ] 3 xO lo x[£0 2 ] 5 . 3Fe=0 2 =S0 2 . 3Gi7 2 <9, 

Voltaite Isometric Fe[Fe 2 ~\^0 6 ^S0 2 ~\± . 2±fi 2 

Phosphates and Arseniates. 
Triphylite Orthorhombic [Fe,Mn,Li 2 \lOsl(PO) 2 , 

Vivianite Monoclinic Fe 3 iO^{FO) 2 . 8H 2 0, 

Dufreni:e Orthorhombic 3 I[i^ 2 ]jO G l(PO) 2 . 3R 2 0, 

Cacoxenite Radiated 3 l[i^ 2 ] 2 10 f! I(PO) 2 . 12H 2 0, 

Scorodite Ortborhombic [Fe 2 \W«l(AsO) 2 . 4iZ,0, 

Pharmacosiderite Isometric 3 i[i^ 2 ] 4 xviu0 lb xvm(^6(9)6' 1&-H&: 

Silicates. 
Fayalite (iron olivine) 

Orthorhombic? Fe 2 ^OfSi, 

Ilvaite (Yenite) Orthorhombic ^ 3 ,[^ 2 ]xii(9 12 xii*S'/ 3 ? 
Schorlomite Massive Ca i [_Fe 2 ]xiv0 14 ^y[_ r JY,Si'] 5 i0 3 . 

Compare also Golumbite, Tantalite, and Wolfram (227) and 
(253). 

334. Metallurgy of Iron. — Native iron of meteoric origin 
is not unfrequently found, but it is doubtful whether nntive iron 
of terrestrial origin exists, although instances of its occurrence 
have been reported. The commercial value of the metal is so 
small that only those ferriferous minerals which are at the same 
time rich, abundant, readily accessible, and ea-ily smelted, can 
be utilized as ores. The useful ores, which are all either ox- 
ides, hydrates, or carbonates, are distinguished, in the list of iron 
minerals given above, by a difference of type ; and the names 



380 IRON. . [§ 334. 

of the most important varieties of the different ores follow the 
names of the species to which they belong. These ores are 
found either in veins or in beds, associated with rocks of all 
ages and of very various characters, and the value of a given de- 
posit frequently depends quite as much on its association with 
coal and lime, and on its proximity to a commercial centre, as 
on the richness of the ore. Hence the great wealth, which has 
been drawn from the deposits of clay iron-stone in the coal-beds 
of England, an ore which, intrinsically, is comparatively poor. 

All the useful ores of iron, when not anhydrous oxides, are 
converted into this condition by roasting, and the oxides are 
easily reduced to the metallic state by simply heating the roasted 
ore with coal. The smelting process, however, also involves 
the fusion of the other mineral matter (gangue), with which the 
true ore is always mixed. This gangue will seldom fuse by it- 
self, even at the high temperature of a blast furnace, and it is 
almost always necessary to mix the ore with some^wx (usually 
limestone), which will unite with the gangue and form a fusible 
slag. The same end is sometimes attained, or at least an ad- 
vantage is gained, by mixing different ores. 

If the iron is reduced at a comparatively low temperature, as 
in a bloomery forge, the metal separates from the melted slag as 
a loosely coherent, spongy solid, the bloom, and is subsequently 
rendered compact by hammering and rolling while still at a 
welding heat. If the iron is reduced at a high temperature, as 
in a blast furnace, the metal unites with a small proportion of 
carbon and is thereby rendered fusible. Both the fused metal 
and the melted slag then drop together into the crucible of the 
furnace, and there the difference of density determines a perfect 
separation of the two molten liquids. The product of the first 
process is nearly a pure metal, and it called wrought-iron. The 
product of the second process contains a variable amount of 
carbon (from 2 to 5 per cent), and is known as cast-iron. 

With the outward aspects of these two varieties of iron every 
one is familiar. Wrought-iron is so soft that it can be readily 
worked with files and other steel tools. It is very tough, and 
has great tenacity. It is exceedingly ductile and malleable. It 
readily fuses before a compound blow-pipe, and in small quanti- 
ties may even be melted in a wind-furnace. It however requires, 
for its perfect fusion, a full white heat. But at a lower temper- 



§334.] IRON. 381 

ature it becomes soft and pliable, and in this condition can be 
wrought or welded on an auvil. It has a fibrous structure, but 
this is in a great measure due to the mechanical treatment it 
receives. 

Cast-iron, on the other hand, has a granular or crystalline 
structure. It is much harder than wrought-iron, and propor- 
tionally more brittle. It is therefore neither malleable nor duc- 
tile, and cannot be wrought on the anvil like the former metal ; 
but, as it melts at a much lower temperature, it is suitable for 
castings. Cast-iron differs greatly in quality, and the two ex- 
treme conditions are seen in the two commercial varieties known 
as white iron and gray iron. White iron has a brilliant white 
lustre and a lamellar crystalline fracture, is very brittle, and so 
hard that it cannot be worked with steel tools. It is, therefore, 
not suitable for casting, but may be used to advantage for mak- 
ing wrought-iron or steel. Gray iron has a darker lustre and 
a more granular fracture. It is much softer, and may be filed, 
drilled, or turned in a lathe. Although less fusible than white 
iron, it flows more freely when melted, and is better adapted 
for casting. It also contains, as a rule, less carbon, but the dif- 
ference of qualities seems to depend more on the condition of 
the carbon than on the amount. In white iron all the carbon 
appears to be chemically combined with the metal, while in 
gray iron the greater part is disseminated in an uncombined form 
through the mass. 1 A form of white iron, called by the Ger- 
mans spiegeleisen (mirror iron), which crystallizes in flat, bril- 
liant tables, and contains about five per cent of carbon, has 
approximately the composition CFe# and another crystalline 
variety has been described, which nearly corresponds to CFe 8 ; 
but the existence of these compounds cannot be regarded as 
proved. Spiegeleisen, moreover, is not a pure ferro-carbide, 
but always contains manganese, the amount varying from 4 to 
12 per cent. Indeed, manganese is a very common ingredient 
of cast-iron, as might be anticipated, seeing that manganesian 
minerals are so frequently associated with iron ores. Cast-iron 
also contains variable quantities of silicon, sulphur, and phos- 

1 When the fracture exhibits large, coarse grains, among which points of 
graphite are distinctly visible, the metal is said to be mottled. Mottled-iron is 
very tough, and is especially valued for casting ordnance. Of all three vari- 
eties of cast-iron, — the white, the mottled, and the gray. — the iron-masters 
distinguish several grades. 



382 IRON. [§334. 

phorus, besides traces of other metals, such as aluminum, cal- 
cium, and potassium. 

By melting cast-iron on the hearth of a reverberatory furnace, 
the carbon and the other impurities may be more or less thor- 
oughly burnt out, and the metal converted into wrought-iron. 
At the same time a portion of the iron is oxidized, and a very 
fusible slag is formed by the union of the oxide with the silica 
always present. 

The metal thickens as it becomes decarbonized, and the 
spongy bloom thus formed is easily separated from the melted 
slag, and hammered or rolled into bars, as before described. 
The greater part of the wrought-iron of commerce is made in 
this way, and the process is called "puddling," because the 
melted metal is stirred or puddled on the hearth of the fur- 
nace in order to expose the mass more effectually to the action 
of the air. The purest iron, thus prepared, siill contains a 
small amount of carbon, which does not, however, impair its 
useful qualities. The other impurities of cast-iron, when not 
wholly removed, render the wrought-iron friable or brittle {short, 
in technical language), and are highly prejudicial. Sulphur 
makes the metal friable while hot (red short), while phosphorus 
and silicon make it brittle when cold (cold short). 

That most valuable form of iron called steel holds an inter- 
mediate position between wrought and cast iron, and partakes, 
to a great extent, of the valuable qualities of both. At a white 
heat it may be worked on the anvil, like wrought-iron, and at 
a higher temperature, but still, within the range of a wind fur- 
nace, it may be melted and cast. If suddenly quenched in water, 
when red-hot. it becomes as hard and brittle as white cast-iron; 
and when subsequently heated to a regulated temperature, the 
temper may be reduced to any desired extent. It may thus 
be made soft and tough, or hard and elastic, at will, and on this 
remarkable quality its numerous and important applications to 
the useful arts depend. Good steel contains from 0.7 to 1.7 
per cent of carbon, and it is made either by carbonizing wrought- 
iron, as in the ordinary cementation method, or, as in the Bes- 
semer process, by decarbonizing cast-iron ; but it is probable 
that the qualities of steel depend fully as much on some un- 
known causes as on the presence of carbon. It has even been 
doubted whether the presence of carbon is essential ; and indeed, 
the whole subject is very obscure. 



§ 335.] IRON. 383 

335. Metallic Iron. — The Sp. Gr. of the purest iron is 8.14, 
but cast-iron has sometimes a specific gravity as low as 7, and 
the den.^ity of the different varieties of the metal ranges between 
these extremes, the average for good bar-iron being 7.7. Iron 
is distinguished for its great susceptibility to magnetism, and in 
this respect it far surpasses both nickel and cobalt, the only 
other metals that exhibit this property in any marked degree. 
The susceptibility of iron to magnetic induction diminishes as 
its hardness increases, but at the same time its power of retain- 
ing the virtue is enhanced. Thus, iron can only be permanently 
magnetized when combined with carbon, as in steel, or with 
oxygen, as in the magnetic oxide or loadstone, Fc s 4 , or with 
sulphur, as in magnetic pyrites, Fe 7 S 8 ; but it is a fact worthy 
of notice, that spiegeleisen, specular iron, Fe 2 O s . and common 
pyrites, FeS 2 , are almost indifferent to the action of a magnet, 
and the same is true of most other iron compounds. 

At a high temperature iron burns readily, and under favor- 
able conditions will sustain its own combustion (63). The 
product formed is Fe 3 4 . At a red heat it also decomposes 
water, yielding the same oxide as before, together with hydrogen 
gas. At the ordinary temperature, however, polished iron re- 
tains its lustre unimpaired, both in dry air and in pure water 
(free from air) ; but when exposed to both air and moisture, 
the surface soon becomes covered with rust. Moreover, this 
change is not merely superficial, but under favorable conditions 
proceeds until the whole mass of the metal is converted into a 
ferric hydrate, having the composition of Limonite. The change 
accelerates as it advances, and the rust first formed seems to 
act as a carrier of oxygen to the rest of the metal. The cor- 
rosion of wood and other organic fibre, when in contact with 
ru^ty nails, has been explained in a similar way. It is also a 
favorite theory that a coating of rust forms with the metal a 
voltaic combination, which actually decomposes the water pres- 
ent, and this is thought to account for the singular fact that iron- 
rust always contains ammonia. 

Iron readily dissolves in dilute mineral acids, yielding a fer- 
rous salt and hydrogen gas. It also dissolves in aqueous solu- 
tion of carbonic acid if free from air. Concentrated sulphuric 
acid, even when boiled with iron, has but little action upon it. 
Nitric acid, on the other hand, rapidly dissolves the metal with 



384 IRON. [§336. 

evolution of NO. It is a singular fact, however, that the most 
concentrated nitric acid (Sp. Gr. 1.45) not only does not attack 
iron, but so modifies its condition that it may subsequently be 
kept for weeks in acid of the ordinary strength (Sp. Gr. not 
less than 1.35) without the slightest alteration of the polish on 
its surface. This same passive condition may also be induced 
in other ways. 

Iron enters into chemical combination with almost all the 
non-metallic elements, and forms alloys with many of the met- 
als. Corresponding to the three degrees of quantivalence are 
three very distinct classes of compounds : first, the ferrous com- 
pounds, whose radical is a single bivalent atom of iron; secondly, 
the ferric compounds, having a sexivalent radical consisting of 
two quadrivalent atoms of iron ; and lastly, a few very unstable 
salts called ferrates, analogous to the manganates, in which a 
sexivalent atom of iron is the acid radical. The last class of 
compounds, although practically unimportant, are interesting, 
as they indicate the close relationship between iron and man- 
ganese ; but iron differs from all the associated elements in that 
the two radicals Fe^ and [i^ 2 ]= form equally stable compounds, 
and play an equally important part in the mineral kingdom ; 
and this double aspect of the element is one of its most charac- 
teristic and important features. 

336. Ferrous Compounds. — The crystallized ferrous com- 
pounds have, as a rule, a light green color, and ferrous oxide 
imparts the same color to glass (152). The soluble ferrous 
salts have a characteristic styptic taste. They are isomorphous 
with the corresponding compounds of magnesium and zinc, and 
quite as closely allied to them as to those of manganese, cobalt, 
and nickel, — the elements with which iron is classed in the 
scheme of this book. Thus, in nature, ferrous carbonate is as 
intimately associated with the carbonates of magnesium and 
zinc as with the carbonate of manganese, and the four bivalent 
radicals replace each other in almost every proportion, not only 
in the carbonates, but also in the silicates, and in a large num- 
ber of other minerals. In like manner, ferrous sulphate (green 
vitriol), like the sulphates of the same metals, and also those of 
nickel and cobalt, crystallizes with seven molecules of water, 
and forms double salts with the sulphates of the alkaline metals 
(313), (322), (330). The sulphate is the most important of 



§337.] IRON. 385 

the soluble ferrous salts, but all the following are also well 
known : — 

Ferrous Chloride FeCJ 2 . UI 2 0, 

Ferrous Nitrate Fe~-0 2 =(N0 2 ) 2 . 0>H 2 O, 

Ferrous Sulphate Fe=0.fS0 2 . (7, 4, 3, or 2H 2 0), 

Ferrous Oxalate Fc = 0./C 2 2 . 2H 2 0, 

Ferrous Phosphate /4i^ 2 IOJ(P<9) 2 . 

In solutions of the ferrous salts, when protected from the air, 
the alkaline hydrates give a white precipitate of ferrous hydrate, 
Fe^O^H 2 , and the alkaline carbonates a similar white precipi- 
tate, which is a hydro-carbonate of variable composition. In 
the presence, however, of a large amount cf NH±Cl, neither 
ammonia nor amnionic carbonate give any precipitate, and the 
precipitation by the other alkaline reagents is in great measure 
prevented. The alkaline sulphides, nevertheless, precipitate 
the iron wholly as a hydrated ferrous sulphide, and so does also 
H 2 S when the solution is alkaline, but not when the slightest 
excess of any mineral acidj^ present. Solutions of the ferrous 
salts, when exposed to th^Pair, absorb oxygen, and the ferrous 
changes into a ferric compound. The same is true of the fer- 
rous precipitates formed/ as just described, all of which are very 
rapidly oxidized as soon as they are exposed to the atmosphere. 
The products in any cage are determined by various conditions, 
but the following are some of the most characteristic of the 
reactions : — 

(4:Fe=0.fS0 2 + 2Hf0.fS0 2 + Aq) + ®=® = 

(2lFe 2 lWJi(80 2 ) 3 + 2B 2 + Aq). [340] 

(20Fe-OfSO 2 + QH 2 + Aq) + 5®=® = [341] 

2(0,x[Fe 2 JfO a =S0 2 . 3M 2 ©) + (^Fe 2 JO G i(S0 2 ) 3 +Aq). 

4Fe=0 2 =M 2 + ®<e) = 20=[Fe 2 J0 4 « 4 . [342] 

337. Ferric Compounds. — Ferric oxide, when dissolved in 
melted borax, imparts to the glass a yellow or yellowish-red 
color, and most of the ferric compounds affect the same tints. 
17 y 



386 IRON. [§337. 

They are isomorphous with the corresponding compounds of 
aluminium, and closely allied to them in their chemical rela- 
tions. The following are the most important of the soluble 
normal salts : — 

Ferric Chloride \_Fe 2 ~\lCJ 6 . 6J7 2 <9, also with 5 or 12ff 2 0, 
Ferric Nitrate \_Fe 2 \lO^(N0 2 ) () . 1S& 2 0, also with \2H 2 0, 
Ferric Acetate \_Fe 2 \lO^{C 2 H z O) Q -f Aq, 

Ferric Sulphate [Fe 2 y=()i(S0 2 ) 3 . 9H 2 0, 
Diammonic-ferric Sulphate 

{NH,) 2 [Fe 2 y«O s ™(SOi) 4 . 2\H 2 0, 
Ferric Oxalate [i^ 2 ]I0J( C 2 2 ) 3 , 

Sodio-ferric Oxalate Na Q .\_Fe 2 ~\ ™ 12 xii( C 2 2 ) 6 . GIIO. 

Ferric acetate cannot be crystallized, and the ferric salts, as 
a rule, crystallize with difficulty. All the well-marked radi- 
cals of the type \_R 2 "1 manifest a very strong tendency to form 
basic compounds (38) [51 J, and the ferric salts furnish a strik- 
ing illustration of the general principle. Most of the native 
ferric salts are basic, and the symbols of a number of such com- 
pounds have already been given. Their mutual relations will 
be best understood if they are studied in connection with the 
various hydrates, from which they may be regarded as derived, 
and a table of the possible ferric hydrates is easily made after 
the principle of (151). Of the compounds which are thus the- 
oretically possible, a large number are easily prepared, and a 
still larger number are at times formed when the conditions 
happen to be favorable; but as the compounds become more 
basic, they soon lose every trace of crystalline structure, and 
with this all evidence of definite chemical constitution disap- 
pears. The products are then amorphous or colloidal solids, 
which present in their composition every possible gradation 
between certain limits. 1 



1 Solutions of various basic compounds are readily obtained eitber by dis- 
solving fresbly precipitated ferric hydrate in a solution of almost any ferric 
salt, or by partially abstracting the acid of the salt by the cautious addition 
of an alkali. A solution of ferric nitrate, for example, may thus be made to 
take up seven additional atoms of [Fe 2 ], On allowing such solutions to evap- 
orate spontaneously, the basic compounds may frequently be obtained in the 
solid state. 



§338.] IRON. 387 

All the more basic salts are, as a rule, insoluble in water, but 
in several cases they affect both a soluble and an insoluble mod- 
ification, and under certain conditions the first changes into the 
last on simply boiling the solution. The soluble condition ap- 
pears in all eases to be a colloidal modification, and by dialys- 
ing (56) a solution of basic ferric chloride it is possible to 
remove almost all the acid radical, and obtain nearly a pure 
solution of ferric hydrate. This solution coagulates on stand- 
ing, and the ferric hydrate thus passes through successive stages 
of dehydration. On boiling the water, the dehydration proceeds 
still further, until at last a hydrate corresponding to Gothite is 
formed. So also the voluminous hydrate, first precipitated by 
alkaline reagents from cold solutions of ferric salts, undergoes a 
similar change under the same conditions. These facts would 
lead us to infer that the " coagulation " of the solutions of the 
basic ferric salts is caused by the elimination of a certain quan- 
tity of water from the molecules of the compound. 

The ferric compounds, although permanent in the air, are 
easily reduced to the ferrous condition by the feeblest reducing 
agent-. 

{[Fe 2 -]Ol 6 + Aq) + Za = (2FeCh + ZnCl 2 -f Aq). [343] 

([Fe] Cl 6 +ff 2 S+Aq) = S+ {2Fe Cl 2 + 2HCI + Aq). [344] 

In solutions of ferric salts, the alkaline hydrates and carbon- 
ates all give a red precipitate of ferric hydrate, whose constitu- 
tion varies with the conditions of the experiment, as indicated 
above. Tins precipitate is insoluble in an excess of sodic or 
potassic hydrate. In the same solutions potassic sulpho-cyanide 
strikes a deep red color, and potassic ferro-cyanide gives a deep 
blue precipitate. These reactions are very delicate, and enable 
us to detect the smallest amount of a ferric compound, even in 
the solution of a ferrous salt. The ferrous compound, under 
the same conditions, gives no color and a white precipitate. 

338. Chlorides. Fe Cl 2 and \_Fe 2 ~\ Cl 6 . — By carefully heating 
crystallized ferrous chloride (336) out of contact with the air, 
the anhydrous compound can be obtained; but a solution of 
ferric chloride cannot be rendered anhydrous by evaporation, 
since the hydrous compound is decomposed by heat into hydro- 
chloric acid and ferric oxide. Anhydrous ferrous chloride can 



S8S 1W% [§339. 

also be obtained by passing UldJl over ignited metallic iron. 
Anhydrous ferric chloride can be prepared in a similar way, 
using ®K91 instead of HKSJl. The first yields a white subli- 
mate ; the second, which is the most volatile, is deposited in 
brownish crystalline scales, and the Sp. Gr. of its vapor has 
been determined. There are fluorides, bromides, and iodides 
corresponding to the chlorides, but they have no special interest. 

339. Oxides. —FeO, [^e 3 ]0 3 , Fe^Fe^niO^. — Ferrous 
oxide may be prepared by boiling in the surrounding water the 
voluminous white hydrate obtained when an alkali is added to 
the solution of a pure ferrous salt, every trace of air being care- 
fully excluded. If exposed to the air, it rapidly absorbs oxy- 
gen, and [jFyOg is the final result. A black pyrophoric pow- 
der, obtained by igniting ferrous oxalate in a close vessel, is a 
mixture of the same oxide with metallic iron. Ferric oxide is 
prepared for the arts by igniting green vitriol, or still better, 
ferric sulphate. It forms, even when most highly levigated, a 
Very hard powder, much used for polishing glass and metallic 
surfaces (Colcothar, Crocus Martis, Rouge). It is also used as 
a red paint. Ferrous-ferric oxide is formed when either of the 
other oxides is intensely heated in the air, and must, therefore, 
be regarded as the most stable of this class of compounds. It 
is distinguished by its susceptibility to magnetism, and its crys- 
talline form (74), which connects it with Spinel (352) and 
other allied isomorphous compounds. Besides the above, one 
or more intermediate oxides have been distinguished, but they 
are probably mixtures of the oxides already named. As has 
been already stated, both the anhydrous and the hydrous oxides 
are abundant native minerals, and important ores. 

340. Sulphides. — The fusible product obtained by melting 
together iron and sulphur, and so much used in the laboratory 
for making H 2 S, is essentially ferrous sulphide, FeS, although 
its composition is not absolutely constant. The same compound 
may be formed by mixing flowers of sulphur and iron-filings 
with water, and, since the resulting compound forms a coherent 
mass, this mixture is useful under certain conditions as a ce- 
ment. Ferric disulphide, FeS 2 (Iron Pyrites), is by far the 
most abundant of the native metallic sulphides. It occurs in 
almost all mineral veins, and is known to the miners as Mundic. 
It is readily distinguished by its yellow color and great hard- 



§341.] QUESTIONS AND PROBLEMS. 389 

ness. The more compact varieties are very resisting minerals, 
but those of a looser texture rapidly crumble when exposed to 
the atmosphere, and this is especially true of the orthorhombic 
variety called Marcasite. The crumbling of many rocks is also 
caused by the oxidation of the pyrites which they contain. Al- 
though useless as an ore of iron, common pyrites is exceedingly 
valuable as a source of sulphur, and for the manufacture of sul- 
phuric acid. The magnetic sulphide Fe 7 S 8 has already been 
mentioned, and there is also a sulphide, Fe 3 S 4 , corresponding to 
the magnetic oxide, and another, Fe 2 S 3 , corresponding to ferric 
oxide. Moreover, sulphides of the composition Fe s S and Fe 2 S 
have been formed, but it is doubtful whether they are all defi- 
nite compounds. The black precipitates, obtained when an 
alkaline sulphide is added to the solutions of ferrous and ferric 
salts, are either sulpho-hydrates (241) or molecular compounds 
of the sulphide and water. They are both very unstable prod- 
ucts, and rapidly oxidize when exposed to the air. 

341. Ferrates. — Potassic ferrate, K 2 =0 2 =Fe0 2 , may be pre- 
pared either by fusing ferric oxide with nitre or by passing 
chlorine gas through a very strong solution of potassic hydrate, 
in which ferric oxide is suspended. Both the fused mass of the 
first reaction, and the black powder deposited from the alkaline 
solution in the second, yield with water a beautiful violet-col- 
ored solution of potassic ferrate. This compound is very un- 
stable, and has merely a theoretical interest. Ferrates of the 
alkaline earths are also known ; but neither ferric acid nor any 
compounds corresponding to the permanganates have as yet 
been discovered. 



Questions and Problems. 

Manganese. 

1. By what simple blow-pipe test may the presence of manganese 
in a mineral be recognized? How far is the color of the manganese 
minerals characteristic ? 

2. Compare the manganous with the niccolous and cobaltous salts, 
and show to what extent they resemble each other, as well as indi- 
cate the points of difference. 

3. Compare the ammonio-salts of the same three elements, and 



390 QUESTIONS AND PROBLEMS. 

seek the cause of the difference of the effects which the atmospheric 
air produces when solutions of these salts are exposed to its influence. 

4. Represent by graphic symbols the constitution both of niangan- 
ous and manganic alum. 

5. Write the reaction of potassic hydrate on a solution of mangan- 
ous chloride, and the further reaction when the resulting precipitate 
is exposed to the atmospheric air. Assume that the final product is 
manganic hydrate. 

6. Write the reaction of hydro-disodic phosphate and amnionic 
hydrate on a solution of manyanous chloride, and also indicate the 
further change which takes place on igniting the resulting precipitate. 

7. Make a list of the oxides of manganese, ami show how far they 
correspond to the oxides of nickel and cobalt on the one side, and 
to those of iron on the other. Make also a similar comparison of the 
different hydrates. Compare also the different oxides and hydrates 
as regards their relative stability. 

8. Of the metals thus far studied, which are precipitated from acid 
solutions, and which only from alkaline solutions, by U 2 S? 

9. By what solvents may the sulphides of manganese zinc and 
cobalt, when precipitated together, be separated ? 

10. In what other way may manganese, when in solution, be sep- 
arated from nickel and cobalt? 

11. To what relationship does the crystalline form of the native 
carbonates of manganese point? 

12. By what means may manganese be separated from zinc when 
both are present in the same solution as acetates ? If they are in 
the condition of chlorides, how may they be readily converted into 
acetates V How far may the same methods be used to separate man- 
ganese from the metallic radicals previously studied? 

13. Write the reaction of the atmospheric oxygen on a solution of 
ammonio-manganous chloride. 

14. Write the reaction of chlorine gas on manganous carbonate 
suspended in water. 

15. Represent by graphic symbols the constitution of Pyrolusite, 
Braunite, and Hausmannite, and endeavor to harmonize the cr)stal- 
lographie relations stated above. Take also into consideration the 
relations of Mn0 2 described in (236). 

16. Represent by graphic symbols the constitution of Manganite 
and Gothite. 

17. Write the reaction of sulphuric and also of hydrochloric acid 
on each of the three oxides, Mn0 2 , il/n 2 3 , and Mn z O v 



QUESTIONS AND PROBLEMS. 391 

18. When a mixture of Mn0. 2 and oxalic acid is heated with di- 
lute sulphuric acid, the products are manganous sulphate water and 
carbonic anhydride gas. Write the reaction, and calculate how 
much C0 2 would be formed for every gramme of Mn0 2 taken. 

19. Ciii jou base on the reaction just written a method of deter- 
mining the purity of the commercial " black oxide of manganese," 
which is frequently a mixture of the different native oxides, and is 
sometimes adulterated with sand. 

20. Assuming that one gramme of a sample of the commercial 
oxide sets free, as above, 0.U54 gramme of CO. z , how much bleaching 
salts cou d be manufactured with 1,000 kilos, of the oxide, assuming 
that the symbol of the bleaching salts is (GVC) = G7 2 ? 

21. Write the reaction of Mn0 2 on HCt -J- Aq, as c uming that 
MnCl± is first lormed and subsequently decomposed by the heat 
employed. 

22. Represent by a graphic symbol the constitution of manganic 
and manganous alum. (332) and (352). 

23. State the distinction between the two classes of manganic 
compounds, and illustrate by representing the constitution of Mn 2 3 
first as a normal sesqu'oxide, and secondly as a molecular compound 
of manganous oxide and manganic dioxide. 

24. Compare tie manganic compounds with the corresponding 
compounds of nickel and cobalt. Consider in this connection the 
relative stability of the substances compared. 

25. Represent the constitution of potassic mangana^e by a graphic 
symbol, and compare this with the graphic symbol of potassic sulphate. 

26. How far does the isomorphism of the sulphates with the man- 
ganates indicate the quantivalence of the metallic radical in these 
compounds? What should you infer from the great difference in 
the stability of the two classes of salts in regard to the sexivalent 
condition of manganese? 

27. Anal\ze reaction [337], and show that it turns on a change 
of quantivalence in the manganese atoms. 

28. Is it necessary to assume a similar change of quantivalence in 
reaction [338]? 

29. Represent the constitution of potassic permanganate by a 
graphic symbo', both on the assumption that the atom-? are octiva- 
lent and also assuming that they are still sexivalent. Can you give 
any reasons why one symbol should be more probable than the 
other? Does not the fact that the permanganates are more stable 
than the manganates have a bearing on the question? How can 
you reconcile the isomorphism of the permanganates and the per- 



392 QUESTIONS AND PROBLEMS. 

chlorates, manganese being an artiad and chlorine a perissad 

element ? 

30. Write the reaction when a solution of manganous chloride is 
boiled with free nitric acid and plumbic dioxide. 

31. How could reaction [339] be used to determine the amount 
of iron in a given solution ? 

32. What do you regard as the chief characteristic of manganese 
as compared with the allied metallic radicals? and why does the s>tudy 
of its compounds have a peculiarly important bearing on chemical 
theories ? 

33. Does not the study of the manganese compounds indicate a 
more rational use of the terminations ous, ic, ite, and ate in the no- 
menclature of chemistry ? 

34. How: may the principles of the nomenclature stated in Chap- 
ter X. be extended so as to express accurately the constitution of the 
more complex chemical compounds ? Give rules based on your own 
experience, and illustrate them by examples. Bear in mind, how- 
ever, that, according to the best usage, the Greek numerals are em- 
ployed, rather than the Latin, as prefixes. 

Iron. 

35. Compare the native compounds of manganese and iron, and 
point out the analogies as well as the differences wh : ch you observe. 

36. Compare in ihe same way the native compounds of nickel and 
cobalt with those of iron, pacing special attention to the sulphides 
and arsenides. 

37. Compare the native compounds of magnesium and zinc with 
those of iron. 

38. The mineral Pisanite indicates what relation between iron 
and copper V 

39. Why is not Pyrites included among the ores of iron ? State 
some of the circumstances on which the value of a bed of iron ore 
depends. 

40. The Sp. Gr. of Pyrites is 5.2, that of Marcasite, 4.7, and that 
of Mispickel, 6.2. Compare the atomic volumes of ihese minerals. 

41. Make a table giving the symbols of the minerals isomorphous 
with Iron Pyrites and Marcasite respectively. 

42. Expla ; n the theory of the " Blast Furnace," 1 and show that 
the formation of slags of the right fusibility is essential to the success 

l See Miller's Chemistry or Percy's Metallurgy 



QUESTIONS AND PROBLEMS. 393 

of the process, and that the proportion of flux must be differently 
adjusted according as cold or hot blast is used. 

43. The slag formed both in the bloomery forge 1 and in the pud- 
dling process 1 is a very fusible ferrous silicate, having approximately 
the composition Fe. 2 s(J=SL Explain the theory of the:>e processes, 
and show that the great fusibility of the slag is an essential condition 
of the prod uc ion of wrought-iron. Cou'd ibe loss of iron in the slag 
be avoided ? How do you account for the low quantivalence of iron 
in this product? To what mineral does it correspond in composition ? 

44. Explain the theory of the Bessemer process 1 for refining cast- 
iron or making steel, and compare it with the pu Idling process. 
Consider especially the effects of the very high temperature attained 
in Bessemer's converter. 

45. Compare together the qualities of iron in its three conditions 
of cast-iron, wrought-iron, and steel. 

46. State the differences between the several varieties of cast-iron, 
gray, mottled, white, and spiegeleisen. 

47. When white iron is dissolved in acid, all the carbon is con- 
verted into a volatile h}dro-carbon oil, while under similar circum- 
stances gray iron leaves a large residue of graphite. What conclu- 
sion do you draw from these facts ? 

48. Write the reaction when iron burns. 

49. Wiite the reaction when steam is passed over red-hot iron. 

50. Write the reaction when iron rusts assumm?, 1st. That the 
metal draws the oxygen wholly from the air; 2d. Tuat water is de- 
composed and ammonia formed. 

51. Write the reaction of an aqueous solution of carbonic acid on 
iron, assuming that no air is present. What is the nature of the solu- 
tion thus obtained (279) ? 

52. Write the reaction of dilute sulphuric acid on iron, and in- 
quire how much the acid should be diluted in order to obtain the best 
effect. In preparing ferrous sulphate, why is it best to u»e ferrous 
sulphide instead of metallic iron? 

53. Write the rational symbol of dipotaesie-ferro'is sulphate, and 
compare its constitution with that of the isomorphous ferrous sulphate 
(336). 

54. Compare the sulphates of magnesd'im, zinc, manganese, and 
iron, as regards the varying quantities of water of crystallization 
with which the several salts may combine. 

1 See Miller's Chemistry or Percy's Metallurgy. 
17* 



894 QUESTIONS AND PROBLEMS. 

55. Pure ferrous nitrate may be obtained by dissolving ferrous 
sulphide in dilute nitric acid. Write the reaction. 

56. When metallic iron is dissolved in dilute nitric acid, the prod- 
ucts are ferrous nitrate, amnionic nitrate, and water. Write the re- 
action and compare it with the last. 

57. Write the reaction of nitric acid (common strength) on iron, 
assuming that the products are feiric nitrate and nitric oxide. 

58. Point out the ferrous and ferric compounds among the symbols 
on pages 378 and 379, and determine in each case the ratio wiiich 
the quantivalenee of the acid radical bears to that of the basic radi- 
cals, both R= and [/? 2 ]1. 

59. Ferrous phosphate is formed by precipitation on adding com- 
mon sodic phosphate to the solution of a ftrrous salt. Write the 
reaction. 

60. Ferrous oxalate is obtained on adding amnionic oxalate to a 
solution of ferrous sulphate. Write the reaction. 

61. Write the reaction which takes rrhce when sodic hydrate is 
added to a cold solution of ierrous sulphate, the air being wholly ex- 
cluded. What further change takes place if the liquid is boiled in 
which the precipitate is suspended? 

62. Write the reaction of amnionic sulphide on a solution of fer- 
rous sulphate, assuming that the precipitate fixes two molecules of 
water. 

63. Write the reaction of sodic carbonate on a solution of ferric 
sulphate, assuming; that the constitution of the product is analogous 
to that formed when the same reagent is added to a solution of mag- 
nesic sulphate. 

64. Write the reaction of sodic carbonate on a solution of ferrous 
chloride, first, when the solution is cold, secondly, when it is boiling. 

65. Ferric hydrat" dissolves in a solution of acid potassic oxalate, 
forming p ta-sin-f rri<* oxalate. Write the reaction. What practical 
application may be made of it ? 

66. Norm d ferric oxalate is precipitated when a slight exee c s of 
any ferric sab is raxed with a solution of amnionic oxalate. Write 
the reaction. The precipitated ferric oxalate readily dissolves in a 
solution of oxalic acid. What compound is probably formed ? When 
this solution is exposed to the sun, ferrous oxalate is precipitated, and 
C0 2 is evolved. Wine the reaction. 

6 7. A so'ution of ferrous carbonate in (C0 2 -f- Aq) deposit", when 
exposed to the air, a hydrate having the composition of Limonite. 
Write the reaction. Under what circumstances might you expect 



QUESTIONS AND PROBLEMS. 395 

that a solution of ferrous carbonate would be formed In nature, re- 
membering that the soil contains more or less ferric hydrate ? Under 
what circumstances would Siderite be deposited from such chal)beate 
waters (279) V Can you form any theory which accounts for the 
formation of beds of Sidexite (clay iron-stone) in connection with the 
coal measures ? 

68. Make a table of the possible ferric hydrates, and point out the 
relations of the native hydratts in your scheme. 

69. By means of the table made as just directed, show in what re- 
lation the different native sulphates, phosphates, and arseniates stand 
to the hydrates. 

70. Mike a table illustrating how many nitrates, s^phates, or 
phosphates may be foimed corresponding to any one of the possible 
hydrates. 

71. Represent by graphic symbols the constitution of the basic 
sulphate 0,\_Fe^U-S0. 2 . 

72. When to the solution of a ferric salt an alkali is added until 
it begins to occasion a permanent precipitate, and the solu'ion is 
then raised to the boiling point, the whole or the. greater part of the 
iron is precipitated as an insoluble basic salt. How do you explain 
the reaction ? 

73. Starting with a molecule of a ferric s<dr, show what products 
would result by the assimilation of successive molecules of ferric 
hydrate. Again, starring with one or more of the complex mole- 
cules thus obtained, and eliminating all the possible molecules of 
water, show what must be the constitution of the basic salts which 
would then be formed. 

74. Have you observed that the solubility of salts in water has 
any connection with the number of atoms of typical hydrogen they 
contain V Cite examples in favor of this theory. 

75. Ci^e different cases in which water is eliminated from a mole- 
cule on boiling the liquid in which the compound is dissolved or 
suspended. 

76. When anhydrous ferrous sulphate is heated to redness, as in 
the process of mnking Nordhausen sulphuric acid (249), it is resolved 
into ferric oxide and into sulphurous and sulphuric anhydrides. 
Write the renction. 

77. The Nordhausen acid is now more frequently msde by distil- 
ling anhydrous ferric sulphate. Write the reaction, and show how 
the sulphate may be tegenerated and the same oxide used over and 
over again. 



396 QUESTIONS AND PROBLEMS. 

78. How could the reactions [343] and [339] be used to deter- 
mine the relative amounts of the two iron radicals in a given mineral, 
assuming that it could be brought into solution without changing the 
atomic condition of* the metal ? 

79. Baric carbonate precipitates all the iron from ferric, but not 
any of the metal from ferrous solutions. Moreover, ferrous hydrate 
precipitates ferric hydrate from the solutions of ferric salts. Write 
these reactions, and discuss the different relations of the two iron rad- 
icals to which they point. 

80. By what characteristic reactions may the atomic condition of 
iron, when in solution, be easily determined ? 

81. Can one condition of iron be said to be more stable absolutely 
than the other ? 

82. What two wholly distinct relationships does iron manifest? 
Trace the lines of connection in each case. Point out also the spe- 
cific characters by which iron is related to each member of the two 
groups of allied elements. 

83. By what character are the elements classed with aluminum 
chiefly marked ? 

84. Compare the reaction of (HCl -(- Aq) on Ni 2 3 , Co 2 O v Mn 2 O s1 
Fe 2 3 , and show ihat the differences depend on the relative stability 
of the several hexad radicals. 

85. In what way may magnesium, zinc, nickel, cobalt, and man- 
ganese be separated from aluminum, chromium, and iron ? 

86. Is there any reason for believing that in crystallized ferric 
chloride the water forms a part of the salt molecule ? Write the 
reaction which takes place when the salt is healed. 

87. Does the Sp. Gr. of anhydrous fenic chloride throw any light 
on the constitution of the ferric salts? 

88. Write the reactions of HKfiH and of Ol-©l on ignited metallic 
iron. Why should a ferrous compound be formed in the firsc case 
when a ferric compound is formed in the second ? 

89. When MnO % is melted into glass colored green by ferrous ox- 
ide, the color is either wholly removed, or, when originally very deep, 
is changed to yellow. How do you explain this reaction, and also 
the other familiar blow-pipe reactions of ferric oxide with a borax 
bead. 

90. Ferric oxide, obtained by drying the hydrate at a temperature 
not exceeding 320°, dissolves easily in acids; but if hea'ed to a low 
red heat, it suddenly glows, becomes denser, and after this dissolves 
in acids with difficulty. Are you acquainted with similar facts in 



QUESTIONS AND PROBLEMS. 397 

regard to any other metallic oxides ? It is observed that the ignited 
oxide dissolves without difficulty in (JrlCl -\~ Aq) when the action is 
aided by ferrous chloride, zinc, stannous chloride, or some other re- 
ducing agent. How do you explain the reaction ? 

91. Write the reaction when FeS 2 is burnt in a current of air, as- 
suming that the products are Fe 2 O z and S0 2 , and calculate how 
much sulphuric acid, Sp. Gr. 1.501, can be made from 1,000 kilos. 
of Pyrites. 

92. In one process of purifying coal gas, the H 2 S is absorbed by 
moist ferric oxide, and the sulphide thus formed is subsequently 
exposed to the air, when the oxide is " regenerated." Explain the 
reaction. 

93. Pyrites appears to be formed in nature by the deoxidation of 
calcic sulphate, by means of organic matter in presence of chalybeate 
waters, and crystals have been formed artificially on twigs, in solu- 
tions of ferrous sulphate. Explain the reaction. 

94. When S0 2 is passed through an alkaline solution of potassic 
ferrate, ferric oxide is precipitated, while potassic sulphate is formed 
in the solu ion. Write the reaction, and show that it may be used 
to determine the constitution of the ferrates. 

95. The slag of a blast-furnace is essentially a double silicate of 
aluminum and calcium, in which the atomic ratio 1 of the two basic 
radicals, Ca= and [^4/ 2 ]l, is one to two. In the less fusible slags the 
total quantivalence of all the basic radicals is equal to that of the sil- 
icon, while in the most fusible slags it is only one half of that amount. 
Write the symbols of these silicates, assuming (as is usually the case) 
that the calcium is partially replaced by magnesium and iron. 

1 By the atomic ratio of a compound is meant the ratio between the total 
quantivalence of the several radicals which it contains. 



398 CHROMIUM. £§ 342 



Division XII. 

342. CHUOMIUM. Cr = 52.2. — Sometime*, although 
rarely, bivalent. Usually either quadrivalent or sexivalent. 
Many of the compounds of this element have a brilliant color, 
and are used as paints, and the name is derived from xp^ a 
(color). The only important native compounds are 

Chromite (Chrome Iron) Isometric .F«?,[CV\Jvi»0 4 , 
Crocoite Monoclinic Pb= 2 = Cr 0. 2 . 

The first is the ore from which all the chrome pigments used in 
the arts are indirectly prepared. It has an iron-black color, 
and has been found in abundance at a few localities, associated 
with serpentine. The second, although a very rare mineral, is 
well known on account of its brilliant red color, and in it the 
element chromium was first discovered (by Vauquelin in 1797). 

343. Metallic Chromium may be prepared by reducing Cr 2 3 
with carbon at a very high temperature, and still more readily 
by reducing Cr 2 Cl 6 with zinc, magnesium, or the alkaline metals. 
On account of its very great infusibility, it has never been ob- 
tained in compact masses, and its qualities are therefore imper- 
fectly known. The whitish-gray porous mass, formed when the 
oxide is reduced by carbon, has a Sp. Gr. of 5.9. It is, like 
cast-iron, a combination of the metal with carbon, and consists 
of grains, which are as hard as corundum. The crystalline 
powder, obtained by reducing the chloride with zinc, has a Sp. 
Gr. of 6.81, and is undoubtedly a purer condition of the metal. 
When in fine powder, chromium takes fire below redness; but 
in its more compact forms it resists oxidizing agents as well as 
aluminum, and acts towards the different mineral acids in a 
similar way. 

344. Chromous Compounds. — This class includes all those 
compounds of chromium in which the element is bivalent; but, 
since its atoms in this condition have still four strong affinities 
unsatisfied, the compounds of this order are all very unstable. 
The most important is CrCh, which is obtained by heating 
Cr 2 Cl G to redness in a current of dry hydrogen. The white 
powder thus formed gives a blue solution with water, which, 
however, rapidly absorbs oxygen, and becomes green when ex- 



§ 345.] CHROMIUM. 399 

posed to the air. Chroraous hydrate, which falls as a dark brown 
precipitate on adding caustic potash to the biue solution, even 
decomposes water with evolution of hydrogen. The most stable 
of the chromous salts is K 2 ,Cr=0 4 =[SOj] 2 • &H 2 0, which forms 
beautiful blue crystals isomorphous with the corresponding fer- 
rous salt. 

345. Chromic Compounds. — In these compounds the ele- 
ment is quadrivalent, but they all contain the sexivalent radical 
[ CrJ. The commercial chromic oxide is a brilliant green pow- 
der, which is very much used in the arts, not only as a common 
paint (chrome green), but also as a verifiable pigment, since it 
imparts a beautiful green color to glass and to the glazing of 
porcelain ware. It may be prepared from the chromates in a 
great variety of ways, as is illustrated by the following re- 
actions : — 

4[Hg 2 ]=0/Cr0 2 = 2[Cr 2 ]© 3 + 8IUg + 5®=®. [345] 

(I\e 4 )/0/Cr 2 5 = [Cr 2 ]0 3 + 4111,® _f- SSN3ST. [346] 

4©il® 2 ,Ol 2 = 2[Cr 2 ]l0 3 + m\-m + ceKD. [347] 

K>0 2 =€i\© 5 + @i-@i = 

[Cr 2 ]I»3 + 2KCI + 2<D<D. [348] 

The first two reactions are obtained by simply igniting the solid 
chromates. The third, by passing the vapor of chloro-chromic 
anhydride through a red-hot porcelain tube, and the last, by 
passing chlorine gas over ignited potassic dichromate. By the 
third reaction the oxide may be obtained in definite rhombohe- 
dral crystals (Sp. Gr. 5.21), which have the form and hardness 
of specular iron, and even the amorphous commercial oxide is 
so hard that, when finely levigated, it may be used like rouge 
for polishing glass. In this hard condition the oxide is almost 
insoluble in acids. There is, however, a less dense condition of 
the oxide (obtained by cautiously heating the hydrate), which 
dissolves freely in all the mineral acids. It has a darker color, 
and, like ferric oxide, changes suddenly with incandescence into 
the insoluble modification, if heated above a definite point. At 
the highest temperatures chromic oxide does not lose oxygen, 
and cannot be reduced by hydrogen. It may be melted by the 
heat of a forge fire, and the molten oxide forms, on cooling, a 
very hard dark-green crystalline solid. 



400 CHROMIUM. .[§345. 

There are a number of chromic hydrates corresponding to the 
ferric hydrates; but the ditferent compounds cannot be isolated 
as readily, and their symbols have not been as accurately deter- 
mined. When sodic or potassic hydrate is added to the solu- 
tion of a chromic salt, the chromic hydrate first precipitated is 
dissolved by an excess of the reagent, but the precipitate reap- 
pears on boiling the liquid. These precipitates retain a portion 
of the alkali, which modifies the qualities of the hydrate, and 
this circumstance renders the investigation of these compounds 
very difficult. The only way to procure a pure hydrate is to 
precipitate with ammonia from boiling solutions. The light- 
blue precipitate thus obtained retains from one to seven mole- 
cules of water, according to the conditions under which it is 
dried. 

The soluble chromic salts affect, as a rule at least, two modi- 
fications. In one state they have a violet color, and crystallize 
more or less readily, while in the other they have a green color, 
and are uncrystallizable. Thus we have, besides an anhydrous 
chromic sulphate, which is red and insoluble, the two following 
hydrous salts: — 

Violet Sulphate (soluble and cryst.) [Or 2 ]I0 6 f(*SU) 3 . 15If 2 0, 
Green " (soluble but uncryst.) [Cr 2 ]W b i(SO,) 3 . hH 2 0. 

The second is obtained by heating the crystals of the first to 
100°. But the water thus driven off cannot be wholly water of 
crystallization, for on simply boiling a solution of the violet 
compound the same change of color and crystalline character 
takes place. There is evidently an essential alteration in the 
molecular structure of the compound, but further than this we 
have as yet no knowledge. 

The best known of the chromic salts is chrome alum, which 
is easily prepared from commercial potassic bichromate by the 
reaction. 

(KfOfOr a 5 + Hf0 2 =S0 2 + SS0 2 + Aq) = . 

(iT 2 ,[0 2 ] vm 8 vm(S0 2 )t + H 2 + Aq). [349] 

This salt, like the other alums, crystallizes with 2ilf 2 in octa- 
hedrons having a dark purple (nearly black) color, but which, 
when sufficiently thin, transmit a beautiful ruby red tint. Care 



§348. J CHROMIUM. 401 

must be taken in reducing the chromate that the temperature 
of the solution does not rise too high, tor above 70° or 80° the 
change above described takes place, and the salt loses its power 
of crystallizing. By keeping, however, the green solution thus 
formed for several weeks, it gradually recovers its violet color, 
and then will yield the normal crystals. 

346. The Chromic Oxalates form two interesting series of 
double salts. Those of the first class have a dark-blue, and 
those of the second class a ruby-red color. Thus we have 

Blue Salt K & 1 2 ] xu 12 »i( C 2 2 ) G . 6ff 2 0, 

Red Salt K 2 [ Cr 2 ] via 8 viii( C 2 0,) 4 . 8B 2 or 1 2H 2 0. 

Ammonia gives no precipitate in solutions of these salts, neither 
does potassic hydrate, until they are boiled. Corresponding 
compounds are known containing (NH 4 ) 2 , Na 2 , Ba, Sr, Ca, or 
Mg in place of A 2 , but with varying quantities of water of crys- 
tallization. 

347. Chromic Nitrate may be obtained in dark purple crys- 
tals having the composition [Cr 2 ]lO tJ i(N0 2 ) 6 . 1SH 2 0, by dis- 
solving chromic hydrate in nitric acid, but the solution becomes 
green and nncrystallizable if heated beyond a limited degree. 

348. Chromic Chloride, [CV 2 ]lC/ 6 , is prepared by passing 
chlorine gas through an intimate mixture of chromic oxide with 
carbon, heated to intense redness in a crucible [126], when the 
chloride sublimes and may be conden.-ed in a second crucible 
covering the mouth of the first. It forms nacreous scales which 
have a beautiful peach-blossom color, and resist the action of 
the strongest acids. They are insoluble in cold water, and even 
in boiling water only dissolve, if at all, very slowly ; but singu- 
larly, on the addition of the smallest quantity of chromous chlo- 
ride, they dissolve immediately, generating much heat, and 
forming a green solution identical with that obtained by dissolv- 
ing chromic hydrate in hydrochloric acid. A solution of the 
corresponding violet chloride may be formed by adding baric 
chloride to a solution of the violet sulphate ; and it is worthy of 
notice that, while from this last solution argentic nitrate precip- 
itates the whole of the chlorine, it only precipitates from a so- 
lution of the green compound one third of its chlorine, unless 
the liquid is boiled. Green crystals having the composition 



402 CHROMIUM. [§ 349. 

[CV 2 "] CIq . 12H. 2 have been described, and compounds of chro- 
mic chloride with the alkaline chlorides are also known. 

Besides the remarkable modifications of the chromic salts de- 
scribed above, mo?t of them manifest a strong tendency to form 
basic compounds, but the principle which they illustrate has 
been already sufficiently discussed (337). 

349. Chlorhydrines. When hydrated chromic chloride is 

dried, it gives off, as the temperature increases, both water and 
hydrochloric acid, and compounds are formed which occupy an 
intermediate position between chromic chloride and chromic 
hydrate, and may be regarded as derived from the former by 
replacing one or more atoms of chlorine with hydroxy 1. Thus 
we have 

Chromic Chloride [ 2 ] I CI & 

Chromic Penta-chlorhydrine [^ 2 ]1C7 5 , Bo . 4J7 2 0, 

Chromic Tetra-chlorhydrine [CfrJlOZi > Ho%, 

Chromic Dichlorhydrine \_Cr 2 ~\lCl 2 , Ho±, 

Chromic Hydrate \_Cr. 2 ~\lBo G . 

The name chlorhydrines is now generally applied to bodies 
of this class, and it can easily be seen that they may be formed 
from water and the anhydrous chlorides by a simple metathesis. 
The compounds, whose symbols are given in (225) and (263), 
may be regarded as having a similar constitution, and the same 
is true of many other oxychlorides, oxyfluorides, &e. 

350. Ckromates or Compounds in which Chromium is Sexiv- 
alent. — These are the most characteristic and important of the 
compounds of this element, and the best known of all is potassic 
dichromate, which is manufactured on a large scale in the arts, 
and extensively used both in dyeing and in the preparation of 
various chrome pigments. It is made from native chrome iron, 
which is reduced to fine powder and roasted on the hearth of a 
reverberatory furnace with a mixture of chalk and potassic car- 
bonate. The mixture is constantly stirred to ha-ten the oxida- 
tion, and the chalk facilitates the change by retaining the mass 
in a porous condition. From the product, water dissolves yel- 
low potassic chromate, which is easily converted into the red 
dichromate by the addition of nitric acid, and the salt is then 



§ 350.] CHROMIUM 403 

separated and purified by repeated crystallizations. There are 
three potassic chromates, all of which yield anhydrous crystals 
easily soluble in water. 

Potassic Chromate (Yellow) K 2 =0 2 =Cr0 2 , 

Potassic Dichromate (Orange Red) K.£-0 2 -Cr 2 0- o , 

Potassic Trichromate (Dark Red) K 2 ^0 2 - Cr 3 8 . 

The normal salt is isomorphous with potassic sulphate. It 
melis when heated, and is not decomposed by simple ignition; 
but when heated with reducing agents it yields chromic oxide 
mixed with some potassic salt. When in solution, it has an 
alkaline reaction, and is converted into the dichromate by the 
weakest acids. The dichromate also fuses without decomposi- 
tion, but whin heated to a high temperature it is converted into 
the normal salt and chromic oxide. In solution it has an acid 
reaction, and on the addition of potassic hydrate changes to the 
normal salt. Both salts possess great coloring power. The 
trichromate has merely a theoretical interest. 

In another process of manufacturing the commercial chro- 
mates the chrome ore is simply roasted with lime. There is 
thus formed the normal calcic chromate, which, although itself 
only partially soluble in water, is converted by digestion with 
dilute sulphuric acid into a dichromate, which is very soluble, 
and from this solution the other chromate may be easily obtained 
by simple metai hetical reactions. The chromates both of cal- 
cium and strontium dissolve readily in dilute acetic acid, while 
baric chromate is insoluble in this reagent ; and on this fact is 
based an important method of qualitative analysis. 

There are two plumbic chromates, which are not only impor- 
tant pigments and dyes, but are also interesting theoretically. 
Their symbols are usually written thus : — 

Plumbic Chromate (Chrome Yellow) Pb=0 2 =Cr0. 2 , 
Diplumbic " (Chrome Orange) (Pb-0-Pb)-0 2 -Cr0 2 . 

The first falls as a brilliant yellow precipitate when a soluble 
chromate is added to a solution of plumbic acetate, and corre- 
sponds to the mineral Crocoite. It melts at a moderate heat, 
forming on cooling a red crystalline solid ; but when strongly 
ignited it is decomposed, and a mixture of the second compound 



404 CHROMIUM, [§350. 

with chromic oxide is the result. The di plumbic chromate has 
a deep orange or red color, according to the mode of prepara- 
tion. The finest vermilion-red is made by fusing the yellow 
chromate with nitre, and washing out the potassium salt with 
water, while an orange color is obtained in dyeing by passing 
the cloth through boiling lime-water, after chrome yellow has 
been fixed in its fibres by steeping it successively in solutions 
of plumbic acetate and potassic bichromate. 

Several other metallic chromates, which are easily prepared 
by precipitation, are used iu painting; but the coloring power 
of the chrome pigments is so great that they are frequently 
adulterated with chalk or some similar white material, and the 
tint is varied by mixing them with other paints. One variety 
of chrome green is a mixture of chrome yellow with Prussian 
blue. 

The chromates are oxidizing agents, and fused plumbic chro- 
mate is sometimes used for this purpose in organic analysis. 
When heated with strong sulphuric acid they evolve oxygen gas 
[230] ; with hydrochloric acid they evolve chlorine, and in both 
Cases chromic salts are formed. 

From the chromates we can easily prepare chromic anhydride, 
CrOz, and the comparative stability of this compound illustrates 
most markedly the chief characteristic of the element chromium. 
The anhydride is most readily obtained by pouring one meas- 
ure of a saturated solution of potassic dichromate into one and 
a half measures of concentrated sulphuric acid. As the liquid 
cools, chromic anhydride crystallizes from it in splendid crim- 
son needles. This beautiful compound is permanent in the air, 
and melts at 190° without undergoing decomposition ; but at a 
higher temperature it gives off oxygen gas, changing first into an 
intermediate brown oxide, Cr z O^ and afterwards into Cr 2 3 . 
It deliquesces in moist air, and dissolves in water in all propor- 
tions. This solution may be regarded as chromic acid, but the 
solution on evaporation yields crystals of the anhydride, and we 
have no evidence that a definite compound is formed. It is a 
very powerful oxidizing agent, and absolute alcohol inflames 
when brought in contact with the crystals. 

Chlorochromic Anhydride, Crl0 2 ,CL, a compound of the 
same type as the last, is distilled when a mixture of potassic 
dichromate, common salt, and sulphuric acid is heated in a glass 



§351.] CHROMIUM. 405 

retort. It is a blood-red volatile liquid, boiling at 118°, and 
yielding a vapor whose Gp. <&t. (5.52) can be easily determined. 
It is at once decomposed by water into hydrochloric acid and 
chromic anhydride, and, like the la>t, is a powerful oxidizing 
agent ; but it is chiefly interesting from its theoretical bearings. 
The existence aUo of CrCI 6 and CrCl A has been inferred from 
certain reactions, but they have never been isolated. 

When potassic dichromate is dissolved in moderately strong 
hydrochloric acid at a gentle heat, there separate, on cooling, 
beautiful orange-colored needles, of a salt whose composition 
may be represented by the symbol Crl0 2 ,CLKo or K~0-{Crl 
2 , C7), and another compound has been obtained whose symbol 
Las been written Crl0 2 ,CLHo . 2H 2 Cl. Their theoretical re- 
lations are obvious. 

Another interesting compound belonging to the type of chro- 
mic anhydride is the fluoride, CrF Q . It distils when a mixture 
of fluor-spar, plumbic chromate, and sulphuric acid are heated 
in a leaden retort, and may be condensed (in a perfectly dry 
leaden receiver kept at a very low temperature) to a. blood-red 
liquid ; but the moment it comes in contact with moist air it is 
decomposed into hydrofluoric acid and chromic anhydride, and 
this reaction is one means of preparing the anhydride in a state 
of purity. 

Lastly, there appears to be a perchromic acid corresponding 
to the permanganic acid. The compound in question is formed 
when to a solution containing peroxide of hydrogen and free 
hydrochloric or sulphuric acid is added a small quantity of some 
chromate. On shaking up the mixture with a few drops of 
ether, this solvent acquires a deep blue color, which is supposed 
to be due to perchromic acid, and the reaction serves as a very 
delicate test for chromium. 

351. Sulphides. — The sulphides of chromium are unimpor- 
tant. The black precipitate formed when amnionic sulphide is 
added to the solution of a chromous salt is probably C?*S. A 
sesquisulphide, Cr 2 S 8 , may also be obtained as a black powder 
by passing II 2 S over ignited Cr 2 Cl G . Like aluminic sulphide, 
it is decomposed by water, and cannot, therefore, be formed in 
an aqueous solution. 



40G QUESTIONS AND PROBLEMS. 

Questions and Problems. 

1. In what order would you classify the elements allied to chro- 
mium, regarding only the stability of the compounds in which they 
act as bivalent radicals? Make a table illustrating this point. 

2. In what order would you classify the same elements, regarding 
alone the stability of the several radicals [/i'oJIV Compare tue qual- 
ities of the several oxides and chlorides of these rad.Cdls. 

3. What is the chief chemical characteristic of chromium ? and 
how is this illustrated by reactions [345] to [348] ? 

4. Can you form any theory as to the cause of the difference be- 
tween the blue and green mouifications of the chromic salts ? Com- 
pare (337). 

5. Blue chromic oxalate is made by boiling a solution of 19 parts 
of potassic diehromate, 23 of potassic oxalate, and 55 of crystallized 
oxalic acid. The red salt is made in the same way with 19 parts of 
the diehromate, and 55 of oxalic acid only. Write the reactions. 

6. What inference would you draw from the peculiar reactions of 
chromic chloride ? 

7. Explain the two methods of making potassic diehromate, and 
illustrate the process by reactions. 

8. Represent by graphic symbols the constitution of the three po- 
tassic chromates. 

9. The p'umbic chromates may all be repre c ented as containing the 
radical (f^P?>.,), including the very rare mineral Plirenicorhroite, 
which contains 23.1 Cr0 3 and 76.9 PbO. Write the symbols of the 
three chromates on this assumption, and weigh their probability as 
compared with those given above. Compare the reactions of the 
plumbic with those of the potassic salts, and consider what bearing 
the general isomorphism of the chromates with the sulphates has on 
the queston (296). 

10. Illustrate by reactions the method of dyeing cloth with chrome 
orange. 

1 1. Write the reaction of s<Tong hydrochloric acid on potassic di- 
ehromate, assuming that the principal products are chromic chloride 
and chlorine gas. 

12. AVhen H.,S is passed through a solution of potassic diehromate 
supersaturated with sulphuric: acid, sulphur is precipitated, and the 
color changes from red to green. Wiite the reaction. 

13. A solution of potassic diehromnte supersaturated with sul- 
phuric acid is much used instead of nitric acid in the porous cup of 



QUESTIONS AND PROBLEMS. 407 

Grove's or Bunsen's voltaic cell (90). What is the theory of its 
action ? • 

14. When a solution of potassic dichromate supersaturated with 
sulphuric acid is boiled with oxalic acid, all the chromic acid is re- 
duced to the condition of a chromic salt, and an equivalent amount 
of CO. i is set free. Write the reaction, and show how it may be used 
to determine the quantity of Cr0 3 in the dicLromate. 

15. The chromium in a soluble chromate may also be estimated as 
sesquioxide. By what reactions may this oxide be separated in a 
condiiiun to be accurately weighed? 

16. How may potassic chromate be used to separate barium from 
calcium and strontium? 

17. It has been found by careful experiment that 10 grammes of 
chromic anhydride yield 7.G048 grammes of chromic oxi.le. We 
know also the Sp. Gr. of chlorochromic anhydiide, and that th's com- 
pound when brought in contact with water undergoes the change 
described above. Deduce the atomic weight of chromium, and state 
the steps in your reasoning. 

18. Write the reaction by which chlorochromic anhydride is ob- 
tained in the reaction described in the text. It may also be made 
by distilling in a small retort a dry mixture of ferric chloride and 
chromic oxide. Write the reaction. 

19. What is the relation of the compound KCr0 3 Cl to potassic 
chromite on the one side, and chlorochromic anhydiide on the 
other ? 

20. Write the reaction by which CrF 6 is obtained in the reaction 
described above. It may also be prepared by distilling a mixture of 
potassic dichromate, ammonic fluoride, and sulphuric acid. Write 
the reaction. 

21. Chromic fluoride is decomposed by glass, and for this reason 
we have not, been able to analyze it, or to determine the density of 
its vapor satisfactorily. Its constitution is inferred from the pro- 
ducts of its reaction with water. Is the conclusion trustworthy ? 

22. Write the reaction of ammonic sulphide on a solution of 
chrome alum. 



408 



ALUMINUM. 



[§352. 



Division XIIL 

352. ALUMINUM. Al = 27.4. — Tetrad, but its com- 
pounds all contain the double atom \_Al 2 \ =. 54.8, which is a 
hexad radical. A. very widely distributed element, and, after 
oxygen and silicon, the most abundant constituent of the rocky 
crust of the. globe, of which it has been estimated that it forms 
about one twelfth. It occurs chiefly in combination with oxy- 
gen and silicon, and most of the siliceous minerals, and rocks, 
when not pure silica, contain aluminum as an essential ingredi- 
ent. For a full enumeration of the aluminum minerals, the stu- 
dent must consult works on mineralogy. The following list 
comprises only such of the more characteristic native compounds 
as illustrate the chemical relations of the element. 



Cryolite 
Chiolite 
Pachnolite 
Thomsenolite 



Fluorides. 



Orthorhombic 
Tetragonal 
Monoclinic 
Monoclinic 



WW 

[Al. 2 ]F 6 



GNaF, 
3NaF, 
3[Ca.Na 2 ~\F 2 .2H 2 0, 



[Al 2 ]F 6 . 2[ Ca,Na 2 ] F 2 . 2H 2 0. 



Oxides. 

Spinel (Ruby) Isometric Mg^Al^^O^ 

Gahnite Isometric Zn^Al^wO^ 

Hercynite Isometric Fe^Al^^O^ 

Corundum, Sapphire, Oriental Ruby, Oriental Topaz, Oriental 
Amethyst, &c. Hexagonal [AL'jlO^ 



Emery 



Massive 



IFe^AQiOs 



Hydrates. 



Gibbsite 


Hexagonal 


XAi^iom* 


Beauxite 


Massive 


fr\Fe 2 M^O?H« 


Diaspore 


Orthorhombic 


Ot[ALyOrir 2 , 


Chrysoberyl 


Orthorhombic 


OHAl 2 y0 2 =G. 



§352.] 



ALUMINUM. 



409 



Sulphates. 

Alunogen Monoclinic [AlJ\ iOJt(S0 2 ) 3 . 18H 2 0, 

Aluminite Massive Of\_Al 2 y0.f{S0 2 ) . $ff 2 0, 

Paraluminite Massive O b x\_Al 2 ]i0 2 ={S0 2 ) . 15H 2 0, 

Aluin-stone (Alunite) 

Rhombohedral K 2 .\_A1 2 ~\ z ™0%p*(S0 2 )z.H u , or 
3(0£\_Al 2 yOiSO. z ) . K 2 =0 2 =S0 2 . 6JI 2 0. 

Octahedral Alums. 

Potassium Alum Isometric K 2 ,[Al 2 y™0 8 ™(SO,) 4 . 24IT>0, 
Ammonium Alum " (iVir 4 ) 2 .[^/ 2 JvmO b vui(^0 2 ) 4 . 2AB 2 0. 

Fibrous Alums. 

Pickeringite Fibrous Mg [Al 2 ~] vm0 8 viH(£0 2 ) 4 . 22F 2 0, 
Apjohnite Fibrous Jf«.[J/ 2 ]vm0 b viii(£0 2 ) 4 . 22# 2 <9, 

Halotrichite Fibrous i^,[^/ 2 J vm 8 vm(^0 2 ) 4 . 22H 2 0. 

Lazulite Monoclinic H 2 ,Mg[Al 2 ~\*-O w xP 2 , 

Turquois Reniform 0^\_Al 2 ~] 2 iOM P0^ 2 < 

Wavellite Orthorhombic lAl^inO^va^PO)^ . 5H 2 0. 





Silicates. 




Andalusite 
Cyanite 


Orthorbombic \ 
Monoclinic ) 


0<Al 2 ]WfSi, 


Topaz 


Orthorbombic 
Feldspars. 


Ff[Al 2 y=0fSi. 


Anorthite 


Triclinic 


Ca,[A^*vnO s ™iSi 2J 


Labradorite 


Tri clinic [A 7 *^. 


CallAl^mO^nSiA 


Leucite 


Isometric 


K 2 [Al/] v,ii O s ™Si 4 4 , 


01i<roclase 


Triclinic [ Ca, N« J .[ Al 2 ~\ viii 0^Si 5 fi , 


Albite 


Triclinic 


JVa. 2 ,[ Al.,] viii O^inS'M, 


Orihoclase 


Monoclinic 


J\ 2 ,[ai 2 ] vui o^sIq o 8 . 



18 



410 ALUMINUM. [§352. 

Clays, 

Kaolinite Orthorhombic H 2 ,\_Al^]™\0 8 ™Si 2 . H 2 0, 

Halloysite Massive H 2 \_Al 2 ~] vmO^S) 2 . ^H 2 0, 

Pyrophyllite Orthorhombic H^Al^vwiO^Si^O^ 

Agalinatolite Massive II^AL^'^O^St^O^ 

Zeolites. 

Thomsonite Orthorhombic [JVa 2 , CW].[^4/ 2 ] via 8 ^Si 2 . 2\H 2 0, 

Katrolite Orthorliumbic Na 2 [Al 2 ]yu\0 8 ^nSi 3 2 . 2H 2 0, 

Scolecite Monoclinic Ca.\ : Al 2 ]^\i0 8 ^iSi 3 2 . 3H 2 0, 

Analcime I-ometric Na 2 ,[Al 2 ]vui0 8 *™Si\O i . 2E 2 0, 

Chabazite Hexagonal Ca,[Al 2 ]vm0^niSi 4 4 . Gff 2 0, 

Harmotome Orthorhombic Ba.\_ A/ 2 ] viii 8 ^S/ 5 6 . hR, 0, 

Heulandite Monoclinic Ca,[A/ 2 ]vm0 8 ""St G 8 . bll 2 0, 

Stilbite Orthorhombic Ca^Al^inO^Si'eQt . QII 2 0. 

To this list may be added the Garnets, the Scapolites, the 
Epidotes, the Micas, and the Chlorites, all large and important 
groups of minerals, which are chiefly silicates of aluminum, but 
which present differences of composition similar to those illus- 
trated above. It is impo sible, however, in the present state of 
the science, to deduce from the results of the analysis of many 
of these minerals any satisfactory or probable rational formula. 
The mineral Lapis Lazuli is a remarkable illustration of this 
fact. It has a definite crystalline form (Fig. 6), and has long 
been used as a paint under the name of ultramarine. It is a 
silicate of aluminum, calcium, and sodium, with a sulphide prob- 
ably of iron and sodium; but numerous analyses have given no 
definite clew either to its rational formula or to the cause of its 
beautiful blue color. Nevertheless, the pigment is now made 
artificially in large quantities, by combining the ingredients in the 
proportions which the analyses have indicated, and this would 
seem to show that it is the theory and not the analysis which is 
at fault. Tiiis subject will be further discussed under silicon. 

It will be noticed that among the native compounds of alumi- 
num are included several of the precious stones, and also Emery, 
which yields an exceedingly hard powder very miK a h used in 
polishing. From the clays the clay slates, and to a less extent 



§353.] ALUMINUM. 411 

from the rarer minerals Alum-stone and Beauxite, the alums 
and other soluble salts of aluminum are prepared. Cryolite, 
now imported from Greenland in large quantities, has become 
an important source of soda-ash. The feldspars, and more im- 
mediately the clays which result from their disintegration, are 
largely used in the manufacture of porcelain and the various 
kinds of earthenware. The coarser clajs furnish the material 
for bricks. The slates, the porphyries, the granites, (he tra- 
chytes, the green stones, the lavas, and other rocks, rich in 
aluminum, are used in building; but the other aluminous 
minerals, with few exceptions, find no important applications 
in the arts. 

353. Metallic Aluminum. — Readily obtained by reducing 
either the chloride or the native fluoride (Cryolite) with metal- 
lic sodium. It has a brilliant white lustre, and possesses to a 
high degree all the qualities of a useful metal^ It has a low 
specific gravity (2.56), but still a very great tenacity. It is 
singularly sonorous. It is very malleable and ductile. It is an 
excellent conductor of heat and electricity. It has a high melting 
point, although somewhat lower than that of silver. It does not 
tarnish in the air, and the molten metal does not oxidize, even 
when heated to a high temperature. Its present value, which 
depends solely on the cost of extraction, greatly limits the ap- 
plications of aluminum in the arts; but, nevertheless, it is used 
to a limited extent for cheap jewelry, and in a few philosophi- 
cal instruments, where it is important to combine lightness with 
strength. An alloy of copper with about ten per cent of pure 
aluminum, called aluminum bronze, has the color of gold, and 
an almost equal power of resisting atmospheric agents. 

Neither sulphuric nor nitric acids, when cold and sufficiently 
diluted, attack aluminum, and nitric acid dissolves it only slowly 
when concentrated and boiling. Hot sulphuric acid, however, 
when not diluted with more than three or four parts of water, 
dissolves it rapidly with the evolution of hydrogen ga*. The 
best acid solvent is hydrochloric acid, which acts on the metal 
at the ordinary temperature even when greatly diluted; but, 
singularly, the metal dissolves almost equally well in a solution 
of cau<tic soda or potash ; and a comparison of the two following 
reactions will make evident one of the most important features 
in the chemical relations of this metal. 



412 ALUMINUM. [§354 

Al-Al + (GB-Cl + Aq) = 

([At-Al]iCl 6 + Aq) + 3HHH. [350] 

Al= Al + {SNao-H +Aq = 

([lfao,i[Al-Al] -j- Aq) + 3H3-HL [351] 

354. Compounds in which \_Al^] is the Basic Radical. — The 
compound- or this class are isomorphous with, and resemble in 
almost every respect, excepting color, the corresponding ferric 
salt. Like the last, they have a great tendency to form basic 
salts, and they exhibit in general the same reactions which have 
been already described (337). The use of the soluble aluminic 
salts in the arts depends, — 1st. Upon their tendency to form 
insoluble basic compounds, and 2d. Upon the fact that these 
basic compounds, including the hydrates, eagerly absorb the 
soluble organic extracts used as dyes. When organic tissues, 
yarn or cloth, are dipped into a solution of a basic aluminic salt 
(compare note to page 386), or when in the process of calico- 
printing a similar preparation is transferred to the surface of 
the fabric in regular designs, the insoluble ba^io compounds, just 
referred to, are formed in the very fibre of the material, and be- 
come still more firmly incorporated when the tissue is exposed 
to the action of air, steam, or other agents in the process known 
as ageing. If now the yarn or cloth thus prepared is dipped 
in a dye-vat, the aluminic compound entangled in the fibre will 
seize and hold the coloring matter, and hence the name of mor- 
dants, from mordeo (to take fast hold of), applied to the-e prep- 
arations of aluminum. The basic, ferric, chromic, and stannic 
salts act in a similar way, and are also used as mordants; but 
while the colorless aluminic salt? take the true color of the dye, 
the others modify the tint to a greater or less extent. Hence, 
in the process of calico-printing, various colors are obtained from 
the same bath, after the design has been printed on the cloth, 
with the appropriate mordants. When salts of aluminum are 
mixed in solution w T ith dye-stuffs, and decomposed by an alka- 
line reagent, the insoluble hydrate or basic salt thus formed 
carries down a large amount of the coloring matter, and these 
colored precipitates, when dried, are used as picrrnents. (Lakes.) 

Of the soluble salts of aluminum, which may be used a* mor- 
dants, the most important are the alums, whose symbols have 



+ 354.] ALUMINUM. 413 

already been given (352). They alone crystallize readily, and 
can therefore be eas.ly manufactured on a large scale in a con- 
dition which insures purity. The alkaline sulphate which they 
contain, al; hough it determines the peculiar crystalline charac- 
ter of the^e double salts, is wholly worthless to the dyer, and it 
depends chiefly on the ruling price whether the amnionic or the 
potassic salt is employed in their manufacture. Sodic alum does 
not crystallize readily, and is therefore never used. The alu- 
minic sulphate, which is the only useful part of the alums, is 
generally obtained by decomposing clay or shale, after it has 
been roa.-ted.at a low red heat with sulphuric acid. It is made 
in large quantities in England and Germany from a bituminous 
shale, found among the lowest beds of the coal measures, which 
contains a large quantity of iron pyrites disseminated through 
the mass. When this alum schist, or alum ore as it is called, 
is slowly burnt, one half of the sulphur of the pyrites is con- 
verted into sulphuric acid, which at once decomposes a portion 
of the alumiuic silicate that the shale contains, thus yielding a 
certain amount of aluminic sulphate. At the same time ferrous 
sulphate is formed by the oxidation of the residue of the pyrites, 
and when the roas:ed mass is lixiviated with water both salts 
dissolve. Lastly, on adding to the solution, after concentration, 
potassic or amnionic sulphate, alum is formed, which is sepa- 
rated from the ferrous salt by crystallization. 

A small amount of potassium alum is made in the Roman 
States from Alum-stone (352). This mineral, when roasted 
and exposed for several months to the action of air and moist- 
ure, crumbles into a sort of mud, which, when lixiviated, yields 
the well-known Roman alum. 

Within the last few years the use of alum has been in a 
measure superseded by the introduction into commerce of pure 
aluminic sulphate, which is made by the direct action of sul- 
phuric acid on some of the purer varieties of clay, and freed 
from iron by means of sodic ferro-cyanide. This reagent is 
added to the solution so long as it occasions a blue precipitate, 
and after this settles the clear liquid is decanted and evapo- 
rated. The residue is known as concentrated alum. The salt 
may be crystallized in small scales, which have the composition 
given below. 

A solution of basic aluminic acetate is also much used as a 



414 ALUMINUM. [§355. 

mordant, especially for madder reds, under the name of red 
liquor. It is prepared by adding plumbic acetate to a solution 
of alum. The only important soluble salts of aluminum, which 
have not yet been mentioned, are the chloride and nitrate. 

Aluminic Chloride [Al^lCl* . UH 2 0, 

Aluminic Nitrate [^ 7 2 ]iOJ(A0 2 ) 6 . \SH 2 0, 

Aluminic Sulphate [Al 2 ]Ws{S0 2 ) 3 . 1SH 2 0. 

The reactions of the aluminic salts, when in solution, differ 
from those of the corresponding ferric salts chiefly in the fact 
that the white aluminic hydrate, which is precipitated by the 
alkaline reagents, dissolves easily and perfectly in an excess 
of either potassic or sodic hydrate. A compound of aluminum 
may generally be recognized by the blue color, which is obtained 
when the solid, previously moistened with a solution of cobaltic 
nitrate, is intensely heated in the oxidizing flame of the blow- 
pipe.^ 

355. Compounds in which \_A1 2 ~\ is the Acid Radical. — So- 
dic aluminate, the same compound which is formed by [351], 
is now manufactured on a large scale from Beauxite. The pul- 
verized mineral, mixed with sodic carbonate, is heated to bright 
redness, and the soluble aluminate thus formed separated from 
the insoluble residue by lixiviation and filtration. On evapo- 
rating the clear solution (in vacuo), a white amorphous solid is 
obtained, which has the composition already given. From so- 
lutions of this compound aluminic hydrate is precipitated on the 
addition of any solulle acid, or even on exposure to the carbonic 
acid of the atmosphere, and this new commercial product may 
be used with great advantage as a substitute for alum. A re- 
markable reaction occurs, when solutions of aluminic chloride 
and sodic aluminate are mixed together in atomic proportions, 
illustrating the singular twofold relations which the radical 
\_A1^\ may sustain. 

([Al^WI, + JSfafiO^Al^ + 6V 2 + Aq) = 

2[-44]I0#flS + (QNaOl + Aq). [352] 

Although other aluminates may be prepared, the salt just 
described is the only noteworthy example of this class of com- 
pounds. Spinel, however, and the allied minerals, may be 
regarded as meta-aluminates.' 



§358.] QUESTIONS AND PROBLEMS. 415 

356. Aluminic Chloride, [\4/ 2 ]f (%, is the only compound of 
aluminum with chlorine. It is made by passing chlorine gas 
into a mixture of aluminic oxide with carbon, heated intensely 
in an earthen retort, when the chloride dist.ls over and cou- 
denses in the receiver in yellowish-white crystalline scales. It 
is a fusible solid, which volatilizes at a temperature only a few 
degrees above its melting-point, and the Sp. Gr. of its vapor 
confirms the theory of its constitution generally accepted. It 
eagerly unites with water, but, like ferric chloride, it cannot be 
recovered by evaporation when once dissolved. It forms double 
salts with the alkaline chlorides, and one of these, \_AI^\ICIq . 
2NaCl, plays an important part in the preparation of aluminum. 

357. Aluminic Oxide, Al 2 3 , forms, as we have seen, the 
mineral Corundum. It may be obtained artificially by igniting 
either ammonia^ alum, or the hydrate obtained indirectly from 
Beauxite (352). It is a hygroscopic white powder, which ad- 
heres to the tongue, but does not become plastic when mixed 
with water. It affects, like ferric oxide, two conditions, and the 
change from one to the other is accompanied in like manner 
by a sudden incandescence. It may be fused by the compound 
blow-pipe, and the resulting transparent bead, like corundum, 
has a hardness only inferior to that of diamond. Moreover, 
colored crystals, resembling the ruby and the sapphire, have 
been obtained by art ^ 

358. Aluminic Sulphide, [Al 2 ~\=S R , is formed when finely di- 
vided aluminum is burnt in the vapor of sulphur It is a black 
powder, which is rapidly decomposed by water into H._S and 
\_A1 2 ~\10^Hq. Hence H 2 S does not under any conditions pre- 
cipitate aluminum from solutions of its salts, and the precipi- 
tate obtained with the alkaline sulphides is simply the normal 
hydrate. 

* Questions and Problems. 

1. Why is not the atomic weight of aluminum doubled according 
to the principle of (19) ? 

2. Can the composition of the native fluorides of aluminum be 
expressed by unitary symbols (69) ? Can you devise a process by 
which sodic carbonate may be made from Cryolite ? 

3. Compare together the minerals isomorphous with Spinel (352), 



41 G QUESTIONS AND PROBLEMS. 

(333), (342), and show in what two ways their constitution may be 
expressed. 

4. Compare the crystalline form and hardness of corundum with 
those of the allied sesquioxides. 

5. Compare the native aluminic with the native ferric hydrates, 
and show how many of the po.-sible hydrates are represented among 
the native alum'mic salts. Use the table of ferric hvdrates already 
made (Pro\ 68, Uiv. XI.). 

6. The symbol of Chrysoberyl may be written after the type of 
Spinel. What argument may be urged for the form given above? 

7. Make a table of the known compounds of the two alum types. 

8. On what principle are the aluminic silicates classified, and how 
do the several members of eaeh group differ from each other ? 

9. Determine the atomic ratios between the various radicals in 
the several aluminic salts, sulphates, phosphates, and silicates. Con- 
sider, first, the simple acid radicals, and secondly, the compound acid 
radicals in these minerals. 

10. What inference should you draw from a comparison of the 
symbols of the different aluminum compounds as regards the isomor- 
phism of calcium with the alkaline radicals? 

11. Some varieties of Pyrophyllite closely resemble Steatite. By 
what simple blow-pipe test can the two minerals be distinguished ? 

12. Write the reaction of sodium on sodio-aluminic chloride or 
fluoride, and caleulate how much aluminum can be obtained theo- 
retically for every kilogramme of sodium employed. 

13. How does the Sp. Gr. of aluminum compare with that of the 
other useful metals ? 

14. Write the reaction of nitric acid and that of sulphuric acid on 
aluminum, assuming that nitric oxide is evolved in the first case, and 
hydrogen gas in the second. 

15. Compare reactions [350] and [351], and point out the differ- 
ent relations of the radical \_AI^\ in the two cases. 

16. Explain the peculiar relations of the aluminic salts on which 
their use as mordants depends. 

17. Write the reaction which takes place when sodic-carbonatc is 
added to a solution of alum, so long as the precipitate first formed is 
redissolved, assuming that in the basic aluminic s^phate, which re- 
mains in solution, the atomic ratio between the basic and acid radi- 
cals (S0 2 ) is as 3 : 1. 

18. What are the relative intrinsic values of potassium-alum, am- 



QUESTIONS AND PROBLEMS. 417 

monium-alum, and crystallized aluminic sulphate, taking as the stand- 
ard the quantity of normal aluminic hydrate which can be obtained 
from each V On what does the preference given to the alums as 
mordants chiefly rest? 

19. Explain and illustrate by reactions the process of manufactur- 
ing alum irom the alum shales, and also from pure clay. 

20. Illustrate by reactions the change of Alum-stone into alum 
in the manufacture of Roman alum. 

21. If a portion of the water obtained in the analyses of Aluminite 
and Paralumimte is water of constitution, how may the symbols be 
written ? 

22. Write the reaction of plumbic acetate on a solution of alum, 
assuming that in the basic acetate, which remains in solution, the 
atomic ratio is 3 : 1. 

23. What are the two chief differences between the chemical rela- 
tions of iron and aluminum? Illustrate the differences by reactions. 

24. Explain and illustrate by reactions the method of manufactur- 
ing sodic aluminate. By what test could you determine when all 
the soda has been converted into sodic aluminate ? Why evaporate 
solution in vacuo? 

25. Write reaction of C0 2 on solution of sodic aluminate, and ex- 
plain the use of this salt as a mordant. 

26. Analyze reaction [352]. 

27. Show how Spinel could be derived from a tetrabydro-magne- 
sic aluminate. 

28. Write the reaction by which aluminic chloride is formed, and 
show that the Sp. Gr. of its vapor confirms the theory of its consti- 
tution generally accepted. 

29. Write the reaction which takes place when a solution of alu- 
minic chloride is evaporated to dryness. Consider whether the pro- 
duct formed by the union of the anhydrous chloride with water ought 
to be regarded as a chemical compound, and, if so, endeavor to rep- 
resent its constitution by a rational symbol. 

30. Compare the reactions of ammonic sulphide on an aluminic 
and on a ferric salt, and explain the cause of the difference. 

31. In what order would you classify the several radicals [-K 2 ]i> 
regarding their electro-negative relations ? 



13 ; 



418 THE PLATINUM METALS. - [§359. 



Divisions XIV. to XVI. 

350. THE PLATINUM METALS. — The six metals 
■which follow aluminum in our classification (Table II.) are al- 
ways found in the native state, although more or less alloyed 
with each other. "Platinum Ore" is found in several coun- 
tries, but at least nine tenths of the commercial supply comes 
from the Ural. It is everywhere obtained by washing alluvial 
material, generally in small rounded metallic grains, although 
masses of considerable size are occasionally found. The follow- 
ing analyses by Deville and Debray will give an idea of its 
composition : — 





Pt 


Au 


Fe 


Ir 


Rh 


Pd 


Cu 


Ir-Os 


Sand 


Choco 


86.20 


1.00 


7.80 


0.85 


1.40 


0.50 


0.60 


0.95 


0.95 


California 


85.50 


0.80 


6.75 


1.05 


1.00 


0.60 


1.40 


1.10 


2.95 


Oregon 


51.45 


0.85 


4 30 


0.40 


0.65 


0.15 


2.15 


37.30 


3.00 


Australia 


GI.40 


1.20 


4.55 


1.10 


1.85 


1.80 


1.10 


26.00 


1.20 


Iiussia 


76.40 


0.40 


11.70 


4.30 


0.30 


1.40 


4.10 


0.50 


1.40 



In this ore the grains of "Native Platinum," which have a steel- 
gray color, are always more or less mixed with those of a dis- 
tinct mineral species called "Iridosmine," 1 which have usually 
a lighter color, and consi.-t chiefly of iridium and o.-mium, al- 
loyed with small quantities of rhodium and ruthenium. Hence 
from the above analyses the amounts of iridosmine (Ir~Os) and 
sand must be subtracted in order to obtain the composition of 
native platinum proper. 

In the old method of manufacturing platinum, the ore is 
treated with aqua-regia, which dissolves the platinum and the 
metals directly alloyed with it, but does not affect the iridos- 
mine, the titaniferous iron, and other resisting minerals, which 
are irequently mixed with the "Native Platinum." To the so- 
lution thus obtained, when brought into suitable condition, am- 
nionic chloride is added, which precipitates all the platinum 
[17G] as ammonio-platinic chloride. This precipitate, when 
ignited, leaves the metal in a pulverulent condition (platinum 

i Iridosmine is frequently associated with California gold, and is separated 
from it at the Assay Offices in considerable quantities. Being heavier than 
gold it sinks to the bottom of the crucible when the metal is fused. 



§3G0.] RUTHENIUM. 419 

sponge), which is welded into a compact mass by heat and 
pressure. 

In the new method of Deville and Debray the platinum is 
first united to metallic lead, which, as it does not alloy with iri- 
dosmine, separates the platinum from the chief impurities in the 
ore. The lead is subsequently removed by cupellation, and the 
crude platinum purified by melting it in a crucible of lime with 
a powerful oxyhydrogen flame. Indeed, an alloy of platinum 
with a small amount of iridium and rhodium, well adapted for 
chemical vessels, may be obtained directly from the on; by fus- 
ing it with the same flame on a bed of lime, using a small 
amount of lime as a flux. The palladium and osmium present 
are thus volatilized, while the copper and iron form tumble com- 
pounds with the lime. 

From the " platinum residues," as they are termed, the asso- 
ciated metals can only be separated by refined analytical meth- 
ods, and our knowledge of the chemical relations of these rare 
elements is still very imperfect. Necessarily, therefore, they 
must occupy a very subordinate place in an elementary treatise, 
and they are here, as elsewhere, classed together, more in con- 
sequence of their intimate association in nature and resemblances 
as metals, than from any well-defined chemical relationship. 

3G0. RUTHENIUM (Ru = 104 4) is a white metal, very 
hai and brittle, with difficulty fusible before the oxyhydrogen 
blow-pipe. Sp. Gr. when fused 11 to 11.4. It is scarcely at- 
tacked by nitro-muriatic acid, but it is easily oxidized when 
fused with potassic hydrate (especially if a little nitre be added), 
yielding potassic rutheniate, which forms with water an orange- 
colored solution. The pulverized metal heated in a current of 
air rapidly absorbs oxygen, and the oxides cannot be reduced 
by heat alone. 

Five oxides are known, — First, RuO, which has a dark- 
gray color and metallic lustre. It is not acted on by acids, but 
is reduced by hydrogen at the ordinary temperature. Secondly, 
Ru 2 A , which is the product when the metal is oxidized by the 
air. It has a deep-blue color, is also insoluble in acids, and is 
reduced by hydrogen, but only at a higher temperature. The 
corresponding hydrate, \_Ru^]lHo G , which dissolves with yellow 
color in acids, but is insoluble in water or alkalies, is also known. 
Thirdly, Ru0 2 , which is a dark, greenish-blue powder, and the 



420 OSMIUM, [§361. 

hydrate Ru=IIo 4 , which dissolves both in acids and alkalies. 
Fourthly, Ru0 3 , which is the assumed anhydride of the yellow 
rutheniate, formed when the metal is ignited with a mixture of 
potassic hydrate with potassic nitrate or chlorate. This char- 
acteri-tic compound is decomposed, like potassic manganate, by- 
acids and even by organic substances. Lastly, Ru0 4 , which is 
a very volatile golden-yellow crystalline solid, melting at 58° 
and boiling at about 100°. 

Ruthenium forms three chlorides: RuGJ 2 , which is known both 
as an insoluble black crystalline powder and as forming a fine 
blue solution ; [/?// 2 ] 6V 6 , which forms yellow solutions and solu- 
ble compounds with the alkaline chlorides, as \_Ru 2 ~\ Cl 6 . 4tKCl; 
lastly, RuCl 4 < known only in its double salts, RuGl 4 . "2KGI 
and RuCl 4 . 2(NH 4 ) Gl, which, like the corresponding platinum 
salt, crystallizes in octahedrons (366), but appears to be dismor- 
phous, as it forms under certain conditions hexagonal prisms. 

When H. 2 S is passed through a solution of the yellow chlo- 
ride, it partly precipitates the ruthenium as a sulphide, but at 
the same time it partially reduces \_Ru 2 ~]Cl 6 to RuGl 2 , which 
gives to the supernatant liquid a fine azure-blue color. Zinc 
effects the same reduction, and this reaction is very delicate and 
characteristic. 

361. OSMIUM (05=199.2). — In the most compact con- 
dition in which this metal has been obtained, it has Sp. Gr. = 
21.4, and a bluish tinge of color resembling that of zinc. It 
has never been fused, but it slowly volatilizes at the tempera- 
ture at which ruthenium and iridium melt. When finely di- 
vided, it is oxidized by nitric acid, but in its more compact state 
it resists even aqua-regia. When heated in a current of air, it 
oxidizes much more readily than ruthenium, passing at once to 
the highest degree of oxidation, Os0 4 , and forming a volatile 
compound resembling RuO A . Indeed, when in powder, osmium 
is very combustible, and even when compact it takes fire at a 
temperature scarcely exceeding the melting-point of zinc, and 
its strong tendency to form this volatile oxide is the most striking 
character of the element. Its oxides and chlorides correspond 
almost precisely both in composition and chemical relations to 
those of ruthenium. The three lower oxides all form hydrates, 
but have no well-marked basic character. Osmic anhydride, 
Os 3 , is unknown, but potassic osraate, K 2 = 2 = Os G 2 . 2H 2 0, 



§362.] RHODIUM. 421 

can easily be obtained in large rose-colored octahedrons. The 
volatile oxide, Os0 4 , just referred to, forms colorless acicular 
crystals, which are very fusible and freely soluble in water. It 
boils at about 100°, emitting an extremely irritating and delete- 
rious vapor, whose pungent odor, resembling that of chlorine, is 
very characteristic. When pulverized osmium is heated in per- 
fectly dry chlorine gas, there is first formed a blue-black subli- 
mate of Os Cl 2 , and afterwards a red sublimate of Os Cl±. Os- 
mious chloride gives a dark violet-blue solution, while osmic 
chloride gives a yellow solution ; and when exposed to the air, 
the first rapidly changes to the last. By the action of reducing 
agents the change may be reversed. All the chlorides of osmium 
form double salts with the alkaline chlorides. The most inter- 
esting are the compounds corresponding to potassio-platinic chlo- 
ride, OsCl 4 . 2KCI, which forms beautiful red octahedral crys- 
tals, sparingly soluble in water, and [OsJC/q . GKCl . (JH 2 0, 
which resembles a characteristic Rhodium compound mentioned 
below. 

362. RHODIUM {Eh = 104.4) is a very hard grayish- 
white metal, barely fusible in an 0x3 hydrogen flame. Sp. Gr. 
after fusion 12.1. It is imperfectly malleable, but when alloyed 
with platinum may be easily worked. The pure metal is insol- 
uble in acids, although when alloyed, in not too large quantity, 
with platinum, copper, bismuth, or lead, it dissolves with them 
in aqna-regia. .Although unalterable in the air, rhodium com- 
bines both with oxygen and chlorine at a red heat. It is read- 
ily oxidized by fusion with nitre or peroxide of barium. Fused 
with potassic bisulphate, it is converted into soluble rhodio-po- 
tassic sulphate, and when heated with sodic or basic chlorides 
in a current of chlorine gas, it yields various double salts, which 
are likewise easily soluble. 

Although several oxides of rhodium have been distinguished, 
the only one which as yet has been well defined is Rh 2 O s , Rho- 
dic Oxide, and this compound evidently marks the prevailing 
quantivalence of the element. In this condition rhodium, un- 
like the elements with which it is associated, appears to be a 
well-marked basic radical, forming stable salts with several of 
the acids. Thus we have 

Rhodic Hydrate \_Rh 2 ~\W^H^ 

Rhodic Acetate [Rh 2l 1 6 i( C 2 ff 3 0) 6 . 5 H 2 0, 



< 



422 IRIDIUM. [§363 

Ehodie Nitrate [i^ 2 ]i0 6 l(#0 2 ) e . AH.,0, 

Rhodic Sulphite [22AJI0,|(iSf0) a . 6#,6>, 

Rhodic Sulphate lBh,]W 6 %S 2 ) 3 . 12/40, 

Potassio-ihodio Sulphate jS^.[i?AJxii0 12 xii( > S'0 2 ) 6 . 

In like manner the only well-defined compound of rhodium 
and chlorine is [T^J 1 67 6 , a brownish-red, indifferent body, in- 
soluble in all acids and alkalies. A solution of the chloride may 
be obtained by dissolving R,0 3 in hydrochloric acid, and from 
this several well-crystallized soluble double chlorides may be 
prepared, as 

Potassio-rhodic Chloride [£AJ Cl 6 . GKCl . 011*0, 

Sodio-rhodic Chloride \_Rh J C\ . GM CI . 24//, 0. 

They all have a ruby Or rose color, whence the metal takes its 
name, from podov, a rose. 

363. IRIDIUM (/r = 196) is a very hard, white, brittle 
metal. Though even less fu-ible than rhodium, it has been 
melted on lime with the oxy hydrogen flame and by the voltaic 
arc. Sp. Gr. after fusion 21.15. The pure metal is not acted 
on by any acid, but when alloyed with platinum it dissolves in 
aqua-regia. It may also be rendered soluble by fusion with al- 
kaline reagents, under the same conditions as rhodium. Unless 
in very fine powder it does not oxidize when heated in the air. 
It forms two principal oxides, lr 2 3 and IrQ 2 , and the corre- 
sponding hydrates are readily obtained. The hydrates dissolve 
in acids, but do not form definite oxygen salts unless associated 
with oiher ba.-ic radicals. There are also chlorides corresponding 
to the oxides, which form crystalline double salts with the alka- 
line chlorides, closely resembling the similar compounds already 
described. Thus we have 

Potassio-iridous Chloride [7r 2 ] C? G . 6AT7 . 6R 2 0, 
Sodio-iridous Chloride [/r 2 ] C! 6 . QNa CI . 24:11,0, 

which contain the radical [ir 2 ]l, and also 

Potassio-iridic Chloride JrCl 4 . 2KCI, 

Sodio-iridic Chloride IrCl, . 2NaCl . 6H 2 0, 

which contain the radical It% the last class being less soluble 



§364.] PALLADIUM. 423 

than the first. Most of the compounds of iridium have a strong 
coloring power, those containing the radical [/r 2 ]l giving in gen- 
eral green, and those containing the radical Ir= red solutions. 
The iridic compounds are the most stable, but under the action 
of reducing or oxidizing agents one condition of the element 
readily passes into the other, and the changes of color which 
then take place, giving under different conditions beautiful 
shades of purple, violet, and blue, are very striking and char- 
acteristic. Hence the name Iridium, from iris, the rainbow. 
Under certain circumstances this element appears to manifest 
still other degrees of quantivalence, and compounds containing 
both Ir= and IrX have been distinguished, the last acting as an 
acid radical in the product obtained by fusing iridium with nitre, 
which gives, with water, a deep blue solution, and is supposed to 
contain the compound KfOflrO^; but our knowledge on this 
subject is still very imperfect. 

3G4. PALLADIUM (Pd = 10G.G). Sp. Gr. = 11.4.— 
This brilliant white metal resembles platinum more clo-ely than 
either of its associates. Although best known as a subordinate 
constituent of platinum ore, it has also been found (in Brazil) 
native, in ma-ses of considerable size. It is harder than plat- 
inum, has less tenacity, and is not so ductile; but, nevertheless, 
it can be wrought with facility. It cannot be fused in an ordi- 
nary wind-furnace, but before the compound blow-pipe it melts 
more readily than platinum, and if heated on lime is slowly 
volatilized, giving off a green vapor. Like the noble metals, 
its oxides and chlorides are reduced by heat alone. Yet 
when exposed to the air at a low red heat its surface be- 
comes covered with an iridescent film of oxide, which is dis- 
persed, however, at a higher temperature. Palladium is acted 
on by chemical agents more readily than platinum. Though 
only slightly attacked by pure hydrochloric or sulphuric acids, 
it dissolves readily in nitric acid, and also in aqua-regia, or in 
sulphuric acid when mixed with a small amount of nitric acid. 
It is also rendered soluble by fusion with alkaline reagents, un- 
der the same conditions as the preceding metals. 

Palladium differs from the associated elements very markedly 
in that it affects most readily the condition of a bivalent positive 
radical. Thus w r e easily obtain, by dissolving the metal in the 
respective acids, the two following crystalline salts: — 



424 PALLADIUM." [§364. 

Palladious Nitrate (Brown) Pd=0 2 =(N0 2 \, 

Palladious Sulphate " Pd=0./S0 2 . 2H 2 0. 

The corresponding hydrate is precipitated by sodic carbonate 
from solutions of either of these salts as a dark brown powder. 
The oxide PdO, a black powder, is obtained by heating the ni- 
trate to dull redness. The chloride PdCl 2 forms brown hydrous 
crystals, when a solution of the metal in aqua-regia is evapo- 
rated to dryness, and by uniting with other chlorides yields 
definite crystalline salts, as, for example, PdCl 2 . 2KCI, which 
is easily obtained in dull yellow prismatic crystals. 

Palladium also forms another class of compounds in which 
its atoms are quadrivalent; but these are all very unstable. 
The chloride PdCl 4 has never been isolated, but the compound 
PdCl± . 2KCI, which has been obtained in red octahedral crys- 
tals, attests the relationship of this element to those with which 
it is classed. 

But of all the characteristics of palladium the most notewor- 
thy is the power which the metal possesses of absorbing hydro- 
gen gas. It appears from the recent experiments of Professor 
Graham that, in the condition in which it is deposited by elec- 
trolysis, this metal will absorb or "occlude" nearly 1,000 times 
its volume of hydrogen, which amounts to about three fourths 
of one per cent of its weight, and in other cond tions of the 
metal the power of absorption is very great, although not so 
large. The same phenomenon to a less degree has also been 
observed with platinum and iron, and considerable amounts of 
"occluded" hydrogen have been discovered in some of the me- 
teors. The gas thus taken up by these metals is not simply 
mechanically condensed, as when absorbed Ly charcoal, but ap- 
pears to be in a state of partial chemical combination like that 
of a solution or an alloy ; for we find that, while the hydrogen 
is easily expelled by hear, it shows no tendency to escape into 
a vacuum. The gas, however, readily passes through a heated 
palladium or platinum plate by an action similar to dialysis (o7), 
and these metals seem to partake more or less of a colloidal 
condition. By a similar action carbonic oxide passes through 
the iron walls of furnaces, and this class of phenomena, when 
further investigated, will undoubtedly be found to be quite 
general. 



§366.] PLATINUM. 425 

"When a mass of palladium, charged as above described, is 
exposed to the air, it sometimes becomes suddenly heated from 
the oxidation of the hydrogen it contains, and the well-known 
power of platinum, especially when finely divided, as in the 
condition of sponge or the so-called platinum black, to determine 
the union of hydrogen and oxygen, and even to ignite a hydro- 
gen jet, together with a large class of similar effects, may be 
explained on the same principle. 

365. Hydrogenium. — The quantity of hydrogen " occluded" 
by palladium amounts to nearly one equivalent lor each equiv- 
alent of the metal, and produces a marked change in its physical 
qualities. The volume of the metal is increased, its tenacity 
and conducting power for electricity diminished, and it acquires 
a slight susceptibility to magnetism, which the pure metal does 
not possess. From these facts Professor Graham infers that 
the metal charged with gas is a.i alloy of palladium and metallic 
hydrogen, which he prefers to call hydrogenium, and it would 
appear that in this remarkable product the anticipations of 
chemists in regard to the metallic condition of hydrogen have 
been realized. If this inference is correct, and if, as is gener- 
ally the case, the volume of the alloy is equal to the sum of the 
volumes of the two metals, then the Sp. Gr. of hydrogenium 
(deduced from that of the alloy) must be about 2. The chem- 
ical qualities of this alloy are very remarkable. It precipitates 
mercury from a solution of its chloride, and in general acts as a 
strong reducing agent. Exposed to the action of chlorine, bro- 
mine, or iodine, the hydrogen leaves the palladium and enters 
into direct union with these elements. Moreover, from a pal- 
ladium wire charged with the gas, and covered with calcined 
magnesia (to render the flame luminous), the hydrogen burns, 
when lighted by a lamp, like oil from a wick. So far, there- 
fore, as its chemical activities are concerned, hydrogenium bears 
somewhat the same relation to hydrogen gas that ozone bears 
to ordinary oxygen. Palladium plate or wire i> most readily 
charged with hydrogen by making it the negative pole of a gal- 
vanic battery in the process of electrolyzing water. (Fig. 84.) 
366. PLATINUM. Pt = 197.4. Sp.Gr.== 21.5. — The 
extended use of this metal in practical chemistry has made its 
appearance familiar to every student of the science. Platinum 
utensils have been of inestimable value in chemical investiga- 



426 PLATINUM. [§366. 

tions, on account of the infusibility of the metal, and its won- 
derful power of resisting chemical agents. It not only does not 
oxidize when heated in the air, but none of the acids singly act 
upon it, and even aqua-regia dissolves it but slowly. The metal 
is corroded when heated to redness in contact with the caustic 
alkalies or alKaliue earths, especially the hydrates of lithium or 
barium, but the alkaline chlorides, carbonates, or sulphates may 
be fused in platinum crucibles without injuring them. Dry chlo- 
rine has no action on the metal at any temperature, and both the 
oxides and the chlorides are reduced by heat alone. Platinum, 
however, readily alloys wiih several of the other metals, and care 
must be taken to conduct no operations in platinum vessels by 
which a fusible metal may be reduced. Phosphorus and sulphur 
also act on platinum to a limited extent. 

Platinum is very ductde and malleable, and two pieces of the 
metal may be welded together at a white heat, although to melt 
it the temperature of the oxyhydrogen flame is required. 
Melted platinum absorbs oxygen from the air, and, like silver 
(140), spits if suddenly cooled. The same phenomenon has 
been observed with palladium and rhodium. 

Platinum affects the condition both of a bivalent and a quad- 
rivalent radical, but its affinities are at best very feeble. When 
dissolved in aqua-regia the product first formed is probably 
PtCl A . 2HCI, and from this solution a large number of other 
compounds of the same type are easily obtained, and these are 
the most important compounds of this element. We have, lor 
example, 

Bario-platinic Chloride PtC! A . BaCI 2 . 4F 2 0, 

Ma?nesio-platinic Chloride PtCl 4 . MgCl, . GM £ 0, 

Sodio-platinic Chloride PtCl, . 2NaCL C>R 2 0, 

Pota-sio-platinic Chloride PtCl 4 . 2KCI, 

Ammonio-platinic Chloride PtCl A . 2(NH 4 ) CI. 

These salts have all a characteristic yellow color except in the 
few cases where the second basic radical, having itself a strong 
coloring power, modifi"S the result. The barium and sodium 
salts crystallize in prisms. The magnesium salt, and the cor- 
responding compounds of cadmium, zinc, copper, cobalt, and 
manganese, which are isomorphous with it, crystallize in rhom- 



§3G7.] PLATINUM. 427 

bohedrons. The potassium and ammonium salts crystallize in 
regular octahedrons. The hydrous salts are all soluble in water, 
but the last two are nearly insoluble in water, and wholly insol- 
uble in alcohol. They, therefore, can easily be obtained by pre- 
cipitation, and on this fact are based several important methods 
of quantitative analysis. Moreover, compounds of the same 
general type may be formed with almost all the organic bases 
and vegetable alkaloids, and they furnish one of the simplest 
means of determining the molecular weight of such substances 
(68). 

If the solution of platinum in aqua-regia is evaporated over 
a water-bath, the amorphous brownish-red residue (soluble both 
in water and alcohol) may be regarded as PtCl 4 ; but if the tem- 
perature is raised to 20u° one half of the chlorine escapes, and 
the h^oluble greenish-brown solid then obtained is PtCl 2 . Plat- 
inous chloride is not acted on even by nitric or sulphuric acids, 
but, out of contact with the air, it dissolves unchanged in hydro- 
chloric acid, although platinic chloride is formed if air has access 
to the solution. It also combines with other metallic chlorides, 
forming a large number of crystalline salts, as, for example, 

Ammonio-platinous Chloride PtCl 2 . 2(NH 4 )Cl, 

Potassio-platinous Chloride PtCl 2 . 2KCL 

Argento-platinous Chloride Pt Cl 2 . 2 Ay CI, 

Zinco-platinous Chloride PtCl 2 . ZnCl 2 , 

Bario-platinous Chloride PtCl 2 . BaCl z . 2>H 2 0. 

These salts are all readily prepared from the hydrochloric acid 
solution {PtCl 2 . 2HCI -f- Aq), and are generally distinguished 
by a red color. 

367. Platinous Hydrates, Pt=Ho 2 , which is obtained as a black 
powder by digesting platinous chloride with a solution of caustic 
potash, dissolves both in alkalies and acids, but the compounds 
thus formed are very unstable. Platinous nitrite and sulphite, 
however, form crystallizahle double salts with several of the 
more basic radicals. Platinic Hydrate, Pt=IIo 4 , prepared indi- 
rectly from platinic chloride, is also soluble both in acids and 
alkalies. The compounds thus formed are all unstable, those 
in which the element acts as an acid radical being the more 
definite. Platinic sulphate and platinic nitrate, although they 



428 QUESTIONS AND PROBLEMS. "[§367 

have not been crystallized, are easily obtained in solution, the 
sulphate by evaporating a solution of the chloride with sul- 
phuric acid, the nitrate by decomposing the sulphate with baric 
nitrate. Lastly, by cautiously heating the hydrates we can 
obtain the corresponding oxides, but if the temperature exceeds 
a limited degree they are at once completely reduced. 

By acting on different platinum salts with ammonia, a re- 
markable class of compounds have been obtained, which are 
best regarded as salts of platinum bases, and as formed by the 
coalescing of two or more molecules of H 3 N soldered together 
by atoms of Ptr or Pt=, although they probably contain in some 
cases more complex platinum radicals. Similar compounds have 
also been formed with palladium and iridium; but, ah hough 
highly interesting subjects of study on account of their manifold 
types and complex constitution, this new class of ammonia bases 
illustrate no principles not already fully discussed, and for a 
description of them we must refer to more extended works. 



Questions and Problems. 

1. Calculate the percentage composition of platinum ore, elimi- 
nating from the results given in (359) the quantity of iridosmine and 
sand with which the ore is mixed. 

2. Explain the old method of working platinum ore, and illustrate 
the various steps in the process by reactions. To what extent are 
the associated metals precipitated by amnionic chloride ? 

3. Point out the relationship between the platinum metals and 
iron. Compare also these elements with each other, and consider 
especially the characteristics distinguishing the three groups into 
which they have been divided in Tab'e II. 

4. By what characters are the platinum metals as a class chiefly 
marked? Mike a table which will bring into comparison the dif- 
ferent double chlorides of these elements. 

5. Explain, on the principle of dialysis, the transmission of hydro- 
gen gas through the walls of a heated palladium or platinum tube. 

6. Begirding the hydrogen condensed by platinum as chemically 
combined with the metal, cannot you find in this circumstance an 
explanation of ihe enhanced energy of the g*s when in this condi- 
tion. Consider the polarization of the negative platinum plate in a 
voltaic cell as an illustration of the same principle. 



QUESTIONS AND PROBLEMS. 429 

7. Show in what way the platinic salts may be used to determine 
the molecular weight of an organic base, and give an illustration of 
the principle. 

8. Write the reactions by which platinic sulphate and nitrate may 
be prepared. 

9. Write the reaction of a solution of platinic chloride on a solu- 
tion of potassic nitrate. Platinic nitrate is one of the products. 

10. Write the reaction of sodic carbonate on a solution of platinic 
sulphate, assuming that the chief product is platinic hydrate. 

11. Write the reactions by which platinous hydrate may be pre- 
pared. 

12. When platinous chloride dissolves in hydrochloric acid in con- 
tact with the air, what is the reaction ? 

13. Make a scheme illustrating the constitution or relations of the 
more important compounds of the platinum bases. 

14. Explain a method of separating the platinum metals from 
each other. 



430 TITANIUM. [§3G8. 



Divisions XVII. to XIX. 

368. TITANIUM. Ti = 50. — Tetrad. No compounds 
corresponding to a lower degree of quantivalence are with cer- 
tainty known. A comparatively rare element, but not unfre- 
quently associated with iron. The most abundant native com- 
pound is Menaccanite or Titaniferous Iron, whose symbol has 
already been given among the iron ores. This mineral, how- 
ever, is in most cases an isomorjlious mixture of ( Ti~Fe) 3 
and Fe 2 0& sometimes containing also magnesium and manga- 
nese, and thus arise the numerous varieties which have been 
distinguished. The other important compounds are 

Rutile, Brookite, and Octahedrite (2d or 4th System) Ti0 2 , 

Perofckite (Rhombohedral) Ca=0./TiO, 

Sphene (Monoclinic) (Ca-O-Ti)W^SL 

Titanium is also associated with columbium, tantalum, cerium, 
yttrium, and zirconium in a number of rare minerals. 

3G9. Metallic Titanium has never been obtained as a mas- 
sive metal, and its properties are very imperfectly known. As 
formed by decomposing the potassio-titanic fluoride with potas- 
sium it is a dark-green powder, showing under the microscope 
the color and lustre of iron. In this condition it is very com- 
bustible, readily dissolves in hydrochloric acid, and even decom- 
poses water at the boiling-point. 

370. Titanic Chloride, Ti CY 4 , is obtained by passing chlorine 
gas through an intimate mixture of titanic oxide and carbon in- 
tensely heated. It is a heavy, colorless liquid, boiling at 135°, 
and yielding a vapor whose Sp. Gr. = 98.G5. Exposed to the 
air it absorbs moisture, and gradually solidifies, forming a crys- 
talline hydrate which readily dissolves in water. From this 
solution, if sufficiently dilute, almost the whole of the titanium 
is precipitated as a hydrate on boiling, and the same is true of 
the solution formed by dissolving the native oxides (after fusion 
with an alkaline carbonate) in hydrochloric acid. 

371. Titanous Chloride, Ti 2 Cl 6 , is formed by passing a mix- 
ture of Wi®\i and SHU through a red-hot porcelain tube. The 
compound is thus obtained in dark violet scales, which readily 



§376.] TITANIUM. 431 

dissolve in water forming a violet solution, but in contact with 
the air this solution gradually loses its color and deposits titanic 
hydrate. The same color is produced by boiling with tin a so- 
lution of titanic oxide in hydrochloric acid, and this reaction is 
the best test for titanium. The solution of titanous chloride is 
a very powerful reducing agent, which indicates that the radical 
[7Y 2 ]1 is not a stable condition of the element. 

372 Titanic Bromide, and Iodide, TiBr 4 and Til 4 , are fusi- 
ble and volatile crystalline solids, 

373. Titanic Fluoride, Til\, is a fuming, colorless liquid, 
obtained by distilling a mixture of fluor-spar and titanic oxide 
with sulphuric acid. This compound is resolved by water into 
soluble hydro-titanic fluoride and insoluble ti'anic oxy fluoride. 

374. Hydro-titanic Fluoride, TiF 4 . 2HF, is the aeid of a 
large class of salts which are easily made from the solution pro- 
duced as just stated. The ammonium and potassium salts, 
which are the most important, both crystallize in white anhy- 
drous scales. 

375. Titanic Hydrates. — A large number of these hydrates 
have been distinguished, and they affect two very different mod- 
ifications. Those obtained by precipitation with ammonia read- 
ily dissolve in acids, and when heated are converted into the 
anhydride with vivid incandescence. Those obtained by boil- 
ing dilute solutions of the chloride or sulphate are insoluble in 
all acids except strong sulphuric. They give off water more 
readily than the others, and the dehydration is not attended by 
the same incandescence. The composition of these hydrates 
depends on the temperature at which they are dried, and they 
may be regarded as derived from the normal hydrate by the 
method repeatedly illustrated and expressed by the general 
equation 

nTiHo, — mH 2 0= (O m Ti n )Ho 4n _ 2m . [353] 

The two modifications have been obtained in the same degrees of 
hydration, and, so far as known, they are isomeric. Moreover, 
by dialysis a pure aqueous solution of titanic hydrate has been 
procured, which gelatinizes when concentrated, and evidently 
contains the compound in a colloidal condition. 

376. Titanic Oxide, Ti0 2 , is chiefly interesting from the 
fact that it affects three different modifications, which are rep- 
resented in nature by the minerals Eutile, Brookite, and Octa- 



432 TITANIUM. [§377. 

hedrite. These three isomeric bodies differ from each other in 
crystalline form, in density, and in hardness. Rutile, the most 
abundant, has the greatest hardness and density. Its crystals 
are tetragonal and isomorphous with those of Sn0 2 . Brookite, 
which stands next in hardness and density, affects forms of the 
orthorhombic system, which are approximately isomorphous with 
those of Mn0 2 . La-tly, Octahedrite is softer and less dense 
than either of the others, and its crystals, although tetragonal, 
differ essentially from those of Rutile. (Problem 2, page 144.) 
The same differences have been observed in crystals obtained 
artificially by decompo ing TiF 4 or TiCl 4 with steam, and it is 
found that the nature of the product depends on the temperature 
at which the reaction takes place, the hardest and most dense 
crystals being formed at the highest temperature. 

In its densest condition titanic oxide has a red color, and is 
insoluble in all acids ; but the white anhydride, obtained by ig- 
niting titanic hydrate, is converted into a sulphate when heated 
with strong sulphuric acid, and may then be dissolved in water. 
The native oxides, also, may be rendered soluble by fusion with 
alkaline carbonates or bisulphates. It melts before the com- 
pound blow-pipe. 

377. Titanous Oxide. Ti 2 0%, is obtained as a black powder 
when a stream of hydrogen is passed over ignited Ti0 2 . It 
dissolves in sulphuric acid, forming a violet solution, from which 
the alkalies precipitate a brown hydrate. A similar reduction 
takes place, and the same violet color is produced, when Ti 2 is 
dissolved in fused borax or microcosmic salt, and the bead 
heated before the blow-pipe on charcoal in contact with a small 
globule of tin. 

378. Titanic Sulphide, TiS 2 , is formed in large, brass-yellow, 
lustrous scales when a mixture of HI 2 I5 and TiPiCS^ is passed 
through a glass tube heated to incipient redness. It is decom- 
posed by water, and cannot, therefore, be obtained by precipi- 
tation. 

379. Nitrides. — Titanium has a marked affinity for nitro- 
gen, and combines with it in several proportions. When dry 
ammonia gas is passed over TiCl 4 it is rapidly absorbed with 
great elevation of temperature, and the resulting brown-red 
powder has the symbol (iT^iV^ TV) = C/ 4 . This compound, heated 
in a stream of ammonia gas, yields a copper-colored substance, 



§381.] TIN. 433 

which is the nitride Ti z N^ and this, when further heated in a 
current of hydrogen, is converted into a second nitride ( Ti 2 N 2 ?) 
having a golden-yellow color and metallic lustre. A third vio- 
let-colored nitride has the symbol TiN 2 . Lastly, the very hard 
copper-colored cubic crystals sometimes found adhering to the 
slags of iron-furnaces, and formerly mistaken for metallic tita- 
nium, have the composition expressed by the symbol Ti 5 CA T 4 . 

380. TI N. Sn =r 1 18. — Bivalent and Quadrivalent. The 
last is the most stable condition. The only valuable ore of tin 
is the oxide Sn0 2 , called in mineralogy Ca>siterite or Tin 
Stone, and this is found at but few localities, chiefly in Corn- 
wall, Malacca, Bolivia, Australia, Bohemia, and Saxony. This 
element is also an essential constituent of Tin Pyrites [Zn,Fe]i 
[Cu 2 yS 4 =Sn, and is associated with columbium, titanium, zir- 
conium, &c, in a few rare minerals, but its range in nature, so 
far as known, is very limited. 

The metal is obtained by reducing the native oxide with coal; 
but, although in theory so simple, this process is in practice quite 
complicated. The ore requires, previous to smelting, a pro- 
longed mechanical treatment, and in the furnace a large amount 
of metal passes into the slags, which therefore have to be worked 
over. 

381. Metallic Tin has a familiar white color and bright lustre. 
It has a crystalline structure, and the breaking of the crystals 
against each other, when a bar of the metal is bent, produces 
the peculiar sound known as the cry of tin. By slowly cooling 
the fused metal distinct crystals can be obtained, which belong 
to the tetragonal system. The tenacity of tin is feeble, but it 
can readily be rolled and beaten into thin leaves, which are 
well known under the name of tin-foil. Sp. Gr. = 7.3. Melts 
at 222°. Boils at a white heat. Inferior conductor of heat or 
electricity. 

Tin does not tarnish in a moist atmosphere which is free 
from sulphur, but when melted in the air it slowly oxidizes, and 
at a red heat decomposes steam. Hydrochloric acid dissolves 
the metal rapidly, the products being stannous chloride and hy- 
drogen gas. It also dissolves slowly when boiled with dilute 
sulphuric acid, yielding stannous sulphate and liberating hydro- 
gen as before. When the sulphuric acid is concentrated, S0 2 
is evolved and stannous sulphate formed only so long as the tin 
19 BB 



434: TIN. [§ 382. 

is in excess. If the acid is in excess, sulphur separates and the 
product is stannic sulphate. Very strong nitric acid does not 
act on the metal, but when somewhat diluted it converts the 
tin into a white hydrate, insoluble in an excess of the acid. 
Aqua-regia, if not too concentrated, dissolves tin as stannic 
chloride, and the alkaline hydrates and nitrates also act upon it 
at a high temperature. 

Tin unites directly with most of the non-metallic elements, 
and forms alloys with many of the metals. The alloys with 
copper have already been mentioned. Pewter and plumber's 
solder are alloys of tin and lead. Britannia metal, an alloy of 
brass, tin, lead, and bismuth, and the silvering of mirrors an 
amalgam of tin and mercury. On account of its beautiful lustre 
and power of resisting atmospheric agents, tin is much used for 
coating other metals. The common tin ware is made of sheet- 
iron thus protected. 

382. Stannous Chloride. SnCl 2 . — The anhydrous com- 
pound (butter of tin) obtained by heating mercuric chloride 
with an excess of tin, or by heating the metal in hydrochloric 
acid gas, is a fusible white solid with a fatty lustre, soluble in 
water and alcohol. The hydrous salt (tin salts), formed by 
crystallizing the solution of tin in hydrochloric acid, has the 
symbol SnCL 2 . 2H.,0. The pure crystals dissolve perfectly in 
a small amount of water, free from air, but a large amount of 
water produces a partial decomposition. 

{2SnCl, + ZH.,0 + Aq) = 

&n,®M, . 2II 2 + (2HCI + Aq). [354] 

So, also, when the solution is exposed to the air. 

(QSnCt, + 4ff.,0 + Aq) + ®=® — 

2(Sn,OCI 2 . 2I1 2 0) + (2SnCU + Aq). [355] 

The oxychloride, which is milk white and insoluble (even in 
dilute acids), renders the solution in both cases turbid. Free 
hydrochloric acid, tartaric acid, and sal ammoniac prevent the 
decomposition. Owing to the unsatisfied affinities of the tin 
radical, stannous chloride is a powerful reducing agent (277), 
and is much used for this purpose both in the laboratory and 
the dye-house. It also acts as a mordant. Lastly, it forms 
salts with several of the metallic chlorides. 



§383.] j -TIN. 435 

Potassio-stannous Chloride Sn Cl 2 . 2KCI . (1,2, or 3^(9), 
Bario-stannous Chloride SnCl 2 . BaCU . iH z O. 

383. Stannic Chloride, SfiCl^ may be made either by dis- 
tilling a mixture of tin and mercuric chloride, the last being in 
excess, or by heating tin in chlorine gas. It is a colorless, fum- 
ing liquid, boiling at 115°, and yielding a vapor whose Sp. Gr. 
r= 132.7. The liquid, exposed to the air, eagerly absorbs moist- 
ure, and changes into a crystalline solid. When mixed with 
water intense heat is evolved, and a solution formed which yields 
on evaporation rhombohedral crystals of SnCl A . bH 2 0. These 
crystals, dried in vacuo, lose Sff 2 0, and there is reason to be- 
lieve that the remaining 2H 2 are a part of the molecule of the 
salt. If we regard, the atoms of chlorine as trivalent, we can 
easily see that such an atomic group would be possible, for we 
might then have the univalent radical {H-CfcCl) = Hcl re- 
placing Ho, and the symbol of the dried salt would be written 
Sn=Ho 2 Mcl 2 . The same principle may be applied in other 
cases where the violence of the action indicates that a chemical 
union has taken place between an anhydrous chloride and water. 
Such bodies, however, may also be regarded as chlorhydrines 
(340), to which molecules of HCl are united in place of water 
of crystallization. Thus the symbol of the hydrous chloride we 
have been discussing might be written Sn = Gl 2 ,Ho 2 . 2HCI. 

Although stannic chloride forms a clear solution with a small 
amount of water, copious dilution determines the precipitation 
of the greater part of the tin as an insoluble stannic hydrate. 
Heat favors this decomposition, and, on the other hand, the pres- 
ence of a large excess of hydrochloric acid prevents it. Stan- 
nic chloride unites with a considerable number of bodies both 
organic and inorganic, and forms double salts with several of 
the metallic chlorides. Ammonio-stannic chloride, SnC/ 4 . 
2NH±Cl (pink salts of the dyers) is isomorphous with the cor- 
responding compound of platinum. An impure solution of 
stannic chloride, made by dissolving tin in aqua-regia, is also 
extensively used in dyeing for brightening and fixing certain 
red colors. 

There are two bromides and iodides of tin corresponding to 
the chlorides. There is also a stannous fluoride, and although 
stannic fluoride has not been isolated, a large number of double 



436 TIN, [§384. 

stannic fluorides or fluostannates are known, which are isomor- 
phous with the corresponding compounds of titanium and silicon. 

384. Stannous Hydrate. -— The precipitate which falls on 
adding an alkaline carbonate to a solution of stannous chloride 
is said to have the composition Ho.f(Sa.fO). It is soluble in 
both alkalies and acids. Boiled with water or a weak solution 
of potash it is rendered anhydrous, but if boiled wiih a concen- 
trated solution of this alkali it yields potassic stannate and me- 
tallic tin. The moist hydrate absorbs oxygen from the air, and 
acts, like the chloride, as a reducing agent. The only impor- 
tant oxygen salt corresponding to this hydrate is stannous 
sulphate. 

385. Stannic Hydrate, like titanic hydrate, affects both a 
soluble and an insoluble modification. The hydrate precipitated 
■when ammonia is added to a solution of stannic chloride dis' 
solves readily both in acids and alkalies, while that obtained by 
boiling the same solution greatly diluted, or by acting on tin 
with nitric acid, is insoluble in acids, and dissolves le-s readily 
than the first in alkalies. The composition of these bodies 
■varies with the temperature at which they are dried, and they 
are usually distingui.-hed as stannic and meta-stannic hydrates. 
Like ihe corresponding compounds of titanium, they may be 
regarded as derived from a normal hydrate of either class by 
the elimination of successive molecules of water. The salts ob- 
tained by dissolving stannic hydrate in oxygen acids are unim- 
portant. The sulphate is the most stable, but this is completely 
decomposed, and the tin precipitated as meta-stannic hydrate 
•when the aqueous solution is diluted and boiled. The atoms 
Sm form much more stable compounds when they act a-* acid 
radicals. The alkaline stannates crystallize readily, and both 
potassic and sodic stannates, {K or Na).f0.fSnO . AH>0, are 
commercial products much used as mordants. Their t fficacy 
depends on the fact that ammonic chloride and all acids even 
the C0 2 of the atmosphere, decomposes these salts when in so- 
lution, and the stannic hydrate thus precipitated in the fibre of 
the cloth binds the coloring matter. 

The compounds obtained by dissolving meta-stannic hydrate in 
alkaline solvents cannot be crystallized, but are precipitated on 
adding to the solution caustic potash. The potassium salt thus 
obtained, dried at 126°, has the composition K 2 = 0.fSn s 9 . AH 2 0. 



§387.] TIN. 437 

It was formerly supposed that the peculiar qualities of the 
meta-stannic hydrates and the meta-stannates were due to the 
atomic grouping here represented, but this opinion has not been 
sustained by recent investigations. The water represented as 
water of* crystallization cannot be removed without decomposing 
the snlt, and is evidently water of constitution ; so that we have 
good rea-on for writing the symbol H 6 JCxO l0 x(S/i 6 O 5 ) after the 
type of the normal stannates, and we may regard it as an ex- 
ample of the soluble colloidal hydrates, to which we have before 
referred (337). This view harmonizes with the facts that on 
boiling an aqueous solution of this compound meta-stannic hy- 
drate is precipitated, and that by dialysis a solution both of 
meta-stannic and stannic hydrates in pure water may he ob- 
tained. The two classes of compounds are probably isomeric, 
but differ in the degree of molecular condensation. 

3^6. Oxides. — Stannous Oxide, SuO, may be obtained in 
various ways, and its color differs according to the mode of 
preparation. It has a strong affinity for oxygen, and if set on 
fire when dry burns to stannic oxide. 

S;annic oxide has been crystallized artificially, not only in the 
forms of" Tin-stone isomorphous with Rutile, but also in forms 
isomorphous with Brookite. As obtained by igniting the hy- 
drate, or by burning metallic tin, it is an amorphous white pow- 
der. It offers even greater resistance to the action of chemical 
agents than Ti0 2 . It is not attacked by acids even when con- 
centrated. It is not dissolved by fusion with alkaline carbon- 
ates, but is rendered soluble by fusion with caustic alkalies. It 
is al-o taken up when fused with acid potassic sulphate, bat 
separates completely when the fused mass is dissolved in water. 
Moreover, like titanic oxide it is very hard and infusible, but 
unlike that it is reduced to the metallic state when ignited in 
a stream of hydrogen gas. 

Besides SnO and Sn0 2 an intermediate oxide, Sn 2 3 , has 
been distinguished, but it does not form definite salts. Dis.-olved 
in hydrochloric acid it gives with auric chloride the beautiful 
purple precipitate known as Purple of Cassius (147). 

387. Sulphides. — The dark-brown precipitate which falls 
when H 2 S is passed through an acid solution of a stannous salt 
is SnS, and the dull yellow precipitate which forms under the 
same circumstances in a solution of a stannic salt is a hydrate 



438 TIN: ' [§388. 

of SnS 2 . The last of these dissolves readily in solutions of al- 
kaline sulphides, and forms with them dt finite salts. It is also 
soluble in the fixed alkaline hydrates, and in either case is pre- 
cipitated unchanged when the alkali is neutralized with an acid. 
Stannous sulphide, on the other hand, does not form salts with 
the alkaline sulphides, and does not dissolve in solutions of these 
compounds, unless, like the common yellow amnionic sulphide, 
they contain an excess of sulphur, when it is converted into 
SnS 2 , and as such is precipitated on neutralizing the alkali. 
It does, however, dissolve in the fixed alkaline hydrates, but 
when an excess of acid is added to the solution a yellow pre- 
cipitate of SnS 2 falls, containing only one half of the tin present. 

The beautiful yellow flaky material known as mosaic gold, 
and used in painting to imi;a:e bronze, consists of anhydrous 
stannic sulphide, and is obtained by subliming a mixture of tin, 
sulphur, sal-ammoniac, and mercury. There is also a sesqui- 
sulphide, Sn 2 S 3 . 

388. Compounds with the Alcohol Radicals. — These com- 
pounds are very numerous and highly important, theoretically, 
because they establish beyond all doubt the atomic relations of 
tin. Compounds have been obtained coniaining methyl, ethyl, 
and amyl, either singly or associated together. Three com- 
pounds are known containing only tin and ethyl. Putting 
Et = ( C 2 H h ) we have 

Sn=Et 21 (Sn=ffl s )-(Sn=M 3 ), SmEt^. 

All three are colorless oily liquids. The last is the most stable, 
boiling at 181°, and yielding a vapor who^e Sp. Gr. = 116. 
The others cannot be volatilized without decomposition, and 
unite directly with oxygen, chlorine, bromine, and iodine. The 
first, especially, like other stannous compounds, acts a^ a redu- 
cing agent, absorbing oxygen from the air, and precipitins sil- 
ver from a solution of the nitrate. This is the only stannous 
compound known among this class of bodies. In all the others 
the tin atoms exert their maximum atom-fixing power, and they 
may be regarded either as compounds of the radicals (SnEf 2 )- 
or (SnEtz)-, or else as formed from stannic ethide by replacing 
either one or more of the atoms of ethyl by other radicals. 
The following are a few examples : — 



§391.] ZIRCONIUM. 439 

Stanno-diethylic Bromide (SnEt 2 )=Br 2 , 

Stanno-diethylic Oxide (SnEt 2 )=0, 

Stanno-diethjlic Acetate (SnEt.,y0 2 =(C 2 H 3 0) 2 , 

Stanno-diethylic Sulphate (SnEt 2 )=0./S0 2 , 

Stanno-triethylic Cliloride (SnEt R )-Cl, 

Stanno-triethylic Hydrate {SuEf z )-0-H, 

Stanno-triethylic Oxide (SnEf s ) 2 =0, 

Stanno-triethylic Carbonate (SuEt s )=0./CO. 

The methyl and amyl compounds are formed after the same 
analogy, and also others which contain both methyl and ethyl. 
These compounds are either liquids or crystalline solids. The 
chlorides, bromides, and iodides are, as a rule, volatile and spar- 
ingly soluble in water. The oxides and oxygen salts, on the 
other hand, generally dissolve freely in water, and are more 
easily decomposed by heat. The vapor densities of several of 
these compounds are given in Table III., and this list might be 
greatly extended. 

389. ZIRCONIUM. Zr ~ 89.G. — Tetrad. Found only 
in Zircon, Eudialyte, and a few other very rare minerals The 
elementary substance closely resembles silicon. It may be ob- 
tained by similar reactions in three corresponding states, amor- 
phous, crystalline, and graphitoidal. Amorphous zirconium is 
a very combustible black powder. The cry.-tals, Sp. Gr. 4.15, 
resemble antimony in color, lustre, and brittleness, and burn 
only at a very high temperature. The graphitoidal variety 
forms very light steel-gray scales. Zirconium is very infusible, 
is but slightly a f tacked by the ordinary acid-, but hydrofluoric 
acid, and in some conditions aqua-regia, dis.-olve it rapidly. 

390. Zirconic Chloride, ZrC/ A , is a white volatile solid (Sp. 
Gr. = 1 17.fi), which dissolves easily and with evolution of heat 
in water. This solution, or the solution of the hydrate in hy- 
drochloric acid, yields on evaporation a large mass of white 
silky needles, which, when heated, lose water and hydrochloric 
acid, leaving an oxychloride, Zr^O A Cl A . 

391. Zirconic Fluoride, ZrE 4 , is likewise a volatile white 
solid, and forms a crystalline hydrate, ZrF A . 3IJ 2 0, which is 
decomposed by heat, leaving pure Zr0 2 . Zirconic fluoride 
unites with many other metallic fluorides, forming salts which 
are isomorjjhous with the corresponding compounds of silicon, 



440 ZIRCONIUM. [§392. 

titanium, and tin. The following symbols illustrate the known 
types : — 

Cadmio-zirconie Fluoride ZrF 4 . 20dF 2 . eff 2 0, 

Tripotassio-zirconic Fluoride ZrF± . 3KF, 

Dipotassio-zirconic Fluoride ZrF 4 . 2KB 1 , 

Potassio-zirconic Fluoride ZrF 4 . KF . H 2 0, 

Sodio-zirconic Fluoride 2ZrF 4 . oNaF. 

392. Zirconic Hydrate, precipitated from the chloride by 
ammonia, and dried at 17°, has the symbol Z/^Ho 4 . Dried at 
a higher temperature, (ZrO)=H» 2 . It is a yellowish, translu- 
cent, gummy mass, having a conchoidal fracture. The hydrate 
precipitated and washed cold dissolves easily in acids, and, very 
slightly, even in water; but when precipitated from hot solu- 
tions, or washed with hot water, it dis^lves only in concen- 
trated acids. Zirconic hydrate acts both as a ba.-e and an acid. 

There are several zirconic sulphates. The normal salt can 
be crystallized, and the formation of a basic sulphate, which is 
precipitated when a neutral solution of zirconia in sulphuric 
acid is boiled with potassic sulphate, is one of the most charac- 
teristic reactions of zirconium. The salts of zirconium have an 
astringent taste, and the solutions redden turmeric paper. 

The precipitated hydrate is insoluble in caustic alkalies, but 
when precipitated by a fixed alkaline carbonate, or, better, by a 
bicarbonate, it dissolves in an excess of the reagent. The alka- 
line zirconates can be obtained by fusion, and several definite 
crystalline zirconates of the more basic radicals have been 
studied. 

393. Zirconic Oxide (Zirconia), Zr0 2 , is obtained by heat- 
ing the hydrate. Prepared at the lowest possible temperature 
it forms a white tasteless powder soluble in acids ; but when 
heated to incipient redness it glows brightly, becomes denser 
and much harder, and is then insoluble in any acid excepting 
hydrofluoric and strong sulphuric. Zirconia has been crystal- 
lized artificially in the same form as Tin-stone and Rutile. 

The mineral zircon is usually regarded as a silicate of zirco- 
nium, Zr^OfSi, but the symbol may aho be written [Z/',£/]i0 2 , 
arid this view harmonizes with the fact that the crystalline form 
is almost identical with that of Zr0 2 , Sn0 2 , and Ti0 2 . More- 



§394.J QUESTIONS AND PROBLEMS. 441 

over, several isoraorphous varieties of this mineral are known 
(Malacone, Oerstedite, &c.) in which the proportions of Zr and 
Si are quite variable. They are more or less hydrous, and for 
the mo;l part comparatively soft, but, like pure ZrO t , they be- 
come, when heated, exceedingly hard as well as more dense. 

394. THORIUM. Th = 1 15.7.— The mineral Thorite, or 
Orangeite, is essentially a hydrous silicate of this exceedingly 
rare metallic element, which has also been found, but only as a 
subordinate constituent, in Euxenite, Pyrochloie, Monazite, 
Gadolinite, and Ortliite. When Thorite is decomposed by hy- 
drochloric acid a solution of thoric chloride, TltCl^ is obtained, 
from which the caustic alkalies precipitate a hydrate insoluble 
in an excess of the reagent. A similar precipitate is obtained 
with the alkaline carbonates, but this readily dissolves when an 
excess is added to the solution. In the >-ame solution a precip- 
itate is obtained with oxalic acid, potassic sulphate, and potassic 
ferro-cyanide. 

As the above reactions indicate, Thorium is allied in many 
of its properties to the metals of the glucinum and cerium 
groups, but in other respects it resembles more nearly zirco- 
nium, with which it is here associated. The anhydrous oxide 
Tlt0. 2 is a white powder, which glows when heated, becomes 
more dense, and after ignition is insoluble in any acid except 
concentrated sulphuric. It has a high specific gravity, and by 
fusion with borax has been obtained in tetragonal crystals (Fig. 
37) resembling those of Tin-stone, Sn0 2 , and Ruiile, Ti0 2 . 
The anhydrous chloride is volatile, and the hydrated chloride 
forms a radiate crystalline mass like ZrCl A . The chloride may 
be reduced by sodium, and the metal may be thus obtained as 
a gray lustrous powder which readily burns in the air. 



Questions and Problems. 
Titanium. 

1. Compare by means of graphic symbols the composition of Pe- 
rofskite and Menaccanite. Can they be regarded as similarly con- 
stituted ? 

2. Write the reaction by which titanic chloride is made. 

3. According to the experiments of Isidore Pierre, 0.821 5 gramme 

19* 



442 QUESTIONS AND PROBLEMS. 

of TiCl K yield 2.45176 grammes of AqCL Calculate the atomic 
weight of titanium, and state clearly the course of reasoning by 
which the result is reached. Ans. 50.34. 

4. Write the reaction which takes place when a dilute aqueous 
solution of TiCl± is boiled. 

5. Write the reactions which take place when a solution of titanif- 
erous iron in lndrochiorio acid is boiled with tin, and explain the 
use of this reaction as a test for titanium. 

6. Write the reaction by which TIF 4 is prepared, and also show 
how it is decomposed by water. 

7. Represent the constitution of hydro-titanic fluoride by a graphic 
symbol, assuming that F is trivalent. 

8. Represent in a tabular form the possible titanic hydrates. 

9. Do the hydrates of any of the preceding elements present phe- 
nomena similar to thot^e of titanic hydrate? 

10. Write the reaction by wlrch TiS 2 is prepared, and also the 
reactions by which crystals of Ti0 2 may be obtained. 

11. Compare the specific gravities and hardness of the native ti- 
tanic oxides. What would these differences indicate in regard to 
the molecular constitution of these minerals? 

12. Represent by graphic symbols the constitution of the nitrides 
of titanium. 

13. Point out the analogies between titanium and the platinum 
metals. Is titanium in any way related to iron ? 

Tin. 

14. Write the reactions of hydrochloric, nitric, and sulphuric acids 
on metallic tin. 

15. Write, the reaction of stannous chloride on solution of IIgCl 2 . 

16. Write the reaction by which anhydrous SnCl 2 is prt pired. 

17. Anal\ze reactions [354] and [355], and explain the use of 
tin salts as a mordant. 

18. Write the reactions by which anhydrous »SnC7 4 is prepared. 

19. Represent the constitution of hydrous stannic chloride by 
graphic s-yu.bols, and apply the same principle to the interpret ation 
of other similar compounds. 

20. Write the reaction when a dilute aqueous solution of stannic 
chloride is boiled, and explain the u^e of this solution as a mordant. 

21. Write the reaction which takes place when stannous hydrate 
is boiled with a concentrated solution of potassic hydrate. 



QUESTIONS AND PROBLEMS. 443 

22. Make a table exhibiting the possible stannic hydrates, and 
explain the difference between the two classes of these compounds. 

23. Write the reaction which takes place when a dilute aqueous 
solution of stannic sulphate is boiled. 

24. Write the reaction which takes place when a solution of sodic 
stannate is boiled with amnionic chloride. 

25. Represent the const'tution of meta-stannic hydrate by graphic 
symbols, and explain the two opinions which have been entertained 
in regard to it, showing how far they are sustained by facts. 

26 . Write the reaction of II 2 S on a solution of stannous or stannic 
chloride. 

27. Write the reaction which takes place when SnS is dissolved 
in yellow ammonic sulphide, and that which fullows on neutralizing 
the alkaline solvent with an acid. Write also the reactions when an 
alkaline hydrate is used as the solvent. 

28. Point out the analog : es and the differences between tin and 
titanium. By what simple reaction may the two elements be sepa- 
rated when in solution? 

29. How is tin related to the platinum metals? 

30. According to tlie experiments of Dumas, 100 parts of tin, 
when bxidized by nitric acid, y ; eld 127.105 parts of SnO r What is 
the atomic weight of the element, assuming that the oxide has the 
constitution represented by the symbol? Ans. 118.06. 

31. On what facts do the conclusions in regard to the atomicity 
of tin and the constitution of its several compounds rest? 

32. Show that the atomic weight of tin, deduced from the percent- 
age composition and vapor densities of its compounds with the alco- 
hol radicals, agrees with the value given above. Sho^v, also, that 
these compounds fully illustrate the atomic relations of the elements. 

33. State the reasons for classing zirconium and thorium with tin 
and titanium. 

34. Point out the resemblances between zirconium and silicon, 
and give the reasons for classing zircon with tin-stone and rutile. 



444 SILICON. [§395. 



Division XX. 

395. SILICON. Si = 28. — Tetrad. Most abundant of 
the elements after oxygen, forming, as is estimated, about one 
fourth of the rocky crust of the globe. Always found in 
nature united to oxygen either as quartz, Si0 2 < or associated 
with more basic radicals in the various native silicates, many 
of whose symbols have already been given (333) (352). The 
elementary substance may be obtained in three different condi- 
tions, — amorphous, graphitoidal, and crystalline. 

1. By decomposing SiF 4 . 2KF with potassium or sodium, 
or by heating the same metals in a current of the vapor of 
SiCl 4 , silicon is obtained as a dull-brown powder, which soils 
the fingers, and readily dissolves in hydrofluoric acid or a warm 
solution of caustic potash, although insoluble in water and the 
common acids. When ignited it burns brilliantly, but the grains 
soon become coated with a varnish of melted silicon, which pro- 
tects them from the further action of the air. 

2. The brown powder just described, when intensely heated 
in a closed crucible, becomes very much denser and darker in 
color, and afterwards is insoluble in hydrofluoric acid, and does 
not burn even in the oxyhydrogen flame. It does dissolve, 
however, in a mixture of hydrofluoric and nitric acids, or in 
fused potassic carbonate, and it deflagrates if intensely heated 
with nitre. 

3. At the highest temperature of a wind-furnace silicon 
melts, and may he cast into bars which have a crystalline struc- 
ture, a sub-metallic lustre, and a dark steel-gray color. More- 
over, by reducing silicon in contact with melted aluminum or 
zinc the molten metal dissolves the silicon, and afterwards, on 
coolinsr, deposits it in definite crystals. These crystals have a 
reddish lustre and the form of diamond, which they almost rival 
in hardness. 

396. Silicic Anhydride or Silica. Si0 2 . — By far the most 
abundant of all mineral substances. The mineralogists distin- 
guish two principal modification-, Quartz and Opal. Quartz 
crystallizes in the hexagonal system (Fig-. 64 to 67), has a Sp. 
Gr. 2.5 to 2.8. is so hard that it cannot be cut with a file, and 
even in powder is but slightly acted on by hot solutions of caus- 



§397.] SILICON. 445 

tic alkalies. Opal is amorphous or colloidal, has a Sp. Gr. 1.9 
to 2.3, is easily abraded with a file, and dissolves in alkaline so- 
lutions. Each of these mineral species exhibits numerous va- 
rieties, determined by differences of structure or admixtures of 
different bodies. Among those of quartz may be mentioned 
common quartz, milky quartz, smoky quartz, amethyst, chal- 
cedony, carnelian, agate, onyx, flint, hornstone, jasper, sand- 
stone, and sand. Among those of opal we have precious opal, 
common opal, jasper opal, wood opal, siliceous sinter, float-stone, 
and tripoli. These two conditions of SiO.# however, are some- 
times found alternating on the same specimen, and the chalce- 
donic varieties of quartz have frequently the appearance of opal, 
through which state they probably passed in the process of for- 
mation. The opals are more or less hydrous, but the water 
present is usually regarded as unessential. 

Both in its crystalline and in its amorphous condition silica 
is insoluble in water and in all acids excepting hydrofluoric 
acid, which is its appropriate solvent. The heat of the oxyhy- 
drogen flame is required for its fusion, but at this temperature 
it melts to a transparent glass, and may be drawn out into fine 
flexible elastic threads, the fused silica affecting the amorphous 
condition. When added in powder to melted sodic or potassic 
carbonate it causes violent effervescence, and if the silica is pure 
the product is a colorless glass. Unless the silica is in great 
excess the alkaline silicates thus obtained are soluble in water, 
and are generally known as soluble or water glass. They yield 
alkaline solutions, which are very much used in the arts, — 
1. As a cement for hardening and preserving stone; 2. In pre- 
paring walls for fresco-painting; 3. For mixing with soap; and 
4. In preparing mordanted calico for dyeing. The same solu- 
tions can be also made by digesting flints in strong -solutions of 
the caustic alkalies at a high temperature under pressure. 

397. Silicic Hydrates. — If to a solution of an alkaline sili- 
cate in water hydrochloric acid be added gradually, a gelatinous 
precipitate of silicic hydrate is formed, which, in its initial con- 
dition, probably has the composition Ho^Si; but in drying it 
passes through every degree of hydration, and the various hy- 
drates which have been obtained in this and in other ways may 
he represented by the general formula 

nHo.Si — mH 2 = Ho^_ 2m (O m Si n ). [356] 



446 SILICON. " [§398. 

They are all, however, very unstable bodies, some losing water 
at low temperatures, and others very hygroscopic, so that it is 
difficult to obtain definite compounds. 

If, instead of making the experiment as just directed, a dilute 
solution of an alkaline silicate be poured into a considerable ex- 
cess of hydrochloric acid, no precipitate is formed. The whole 
of the hydrate remains in solution mixed with the alkaline chlo- 
rides and free hydrochloric acid. These crystalloid substances, 
however, can readily be separated by dialysis from the colloid 
hydrate, and a pure solution of silicic hydrate may be thus ob- 
tained containing as much as five per cent of S10 2 . Moreover, 
by boiling in a flask the solution may be concentrated, until the 
quantity of silica reaches fourteen per cent. This solu ion is 
limpid, colorless, tasteless, and has a feebly acid reaction, which 
a very small quantity of K~Ho is sufficient to neutralize. 

Evidently, then, silicic hydrate has both a soluble and an in- 
soluble modification, but the last is by far the most stable con- 
dition. The concentrated solution, formed as above, in a few 
days completely gelatinizes. Moreover, even in a closed vessel 
this jelly gradually shrinks, spontaneously squeezing out the 
greater part of the water, until at last it becomes a hard mass 
resembling opal. When, however, the solution is quite dilute, 
it can be kept indefinitely without gelatinizing, and most spring 
and river waters, hold an appreciable amount of silicic hydrate 
thus dissolved. The power of dissolving silica, which natural 
waters possess, is greatly enhanced by the presence of alkaline 
carbonates ; and when the action of the alkaline liquid is aided 
by a high temperature, as in the case of hot springs, large 
quantities of silica are frequently dissolved, and such solutions 
have undoubtedly exerted an important agency in the geolog- 
ical history of the earth. Whenever a solution of silicic hydrate 
is evaporated to dryness, the whole of the silica is rendered in- 
soluble and cannot afterwards be dissolved either in water or 
common acids. 

398. Silicates. — Although it is impossible to- isolate the 
numberless intermediate silicic hydrates comprehended in [356], 
yet we find in nature numerous mineral silicates formed after 
the same types, and which may be regarded as derived from the 
hydrates by replacing the hydrogen atoms with various basic 
radicals. These silicates, like silica itself, affect both the crys- 
talline and the colloidal condition. 



§398.] SILICON. 447 

The crystalline silicates are represented by numerous well- 
defined mineral species, and by the rocks which are simply ag- 
gregates of such minerals. They have been formed in many 
ways; for example, — 1. By deposition from solution; 2. By 
the action of heated water or vapor on igneous and .sedimentary 
rocks; 3. By the slow cooling of molten siliceous material. 

The colloidal silicates are represented by the ob-idians, the 
pitch-stones, and other volcanic rocks, which have probably al- 
ways been formed by the sudden cooling of melted lavas. To 
the last class belong also the various artificial silicates we call 
glass, and the slags obtained in many metallurgical processes. 
Thus crown-glass is a silicate of sodium or potassium with cal- 
cium, flint-glass a silicate of either of tl^e alkaline radicals with 
lead, and the slags silicates of calcium, magnesium, aluminum, 
and iron in various combinations. Since many of the basic hy- 
drates and anhydrides may be melted with silica in almost every 
proportion, we do not find in the colloidal silicates the same 
definite composition as in the crystalline minerals, but they are 
probably in all cases mixtures of definite compounds. 

Most of the silicates are fusible, and their fusibility is in- 
creased by mixture with each other. As a rule, those which 
contain the most fusible oxides melt the most readily, and the 
more readily in proportion as the base is in excess. Only the 
alkaline silicates above referred to are soluble in water. Most 
of the hydrous silicates, and many which are anhydrous but 
contain an excess of base, are decompo-ed by acids; 1 but the 
anhydrous, normal, or acid silicates are, as a rule, unaffected by 
any acid, except hydrofluoric, although they can be rendered 
soluble by fusion with an alkaline carbonate. When the fused 
mass is treated with HGl -\- Aq, evaporated to dryness, and 
again digested with the same acid, the silica remains as a gritty 
insoluble powder, and can at once be recognized. The pres- 
ence of silica in a mineral can generally also be discovered by 
fusing a small fragment before the blow-pipe with microcosmic 
salt. This decomposes the mineral, but does not dissolve the 
silica, which is left floating in the clear bead. 

1 Soluble compounds of the basic radicals are thus formed, while the silica 
separates either as a gelatinous hydrate, or as a loose, anhydrous powder. 
Sometimes, however, the silica also dissolves, and generally it is taken up to 
a limited extent. In every case the silica becomes anhydrous, and completely 
insoluble if the solution is evaporated to dryness at the boiling-point of water. 



448 SILICON. [§399. 

399. Constitution of Native Silicates. — The symbols of' 
many of the native Mlieates have already been given, and those 
of others will be discovered by solving the problems which fol- 
low r this division. Moreover, the principles on which these sym- 
bols are written have been fully developed. There is still, 
however, an uncertainty in regard to the constitution of some 
of these minerals, and it is not always possible to deduce from 
the results of analysis a probable rational formula, even when 
these results are known to be essentially accurate. This uncer- 
tainty arises from several causes: — 1. We have no sure crite- 
rion of the purity of the mineral, since we are not able, as in 
the case of artificial products, to eliminate admixtures by re- 
peated crystallizations ; 2. The methods commonly used to de- 
termine the molecular weight of compounds (66) entirely fail 
in the case of these silicates, and this important element for fix- 
ing the symbol is therefore wanting 1 (23). Moreover, when 
the molecule is condensed (that is, contains several atoms of 
silicon) unavoidable inaccuracies in the processes may vitiate 
conclusions based on analysis alone ; 3. The constant replace- 
ment of one radical by another (214) renders the composition 
of most silicates very complex, and we are frequently at a loss 
to determine the part which a given radical may play in the 
compound. This is especially true of hydrogen, for we have 
no certain means of deciding whether the atoms of this element 
in a hydrous silicate are a part of the molecule itself, or only 
connected with it in the water of crystallization. 

400. Symbols of Native Silicates. — The composition of most 
native silicates may be so varied by replacements, without any 
essential change in external qualities, that such a mineral spe- 
cies cannot be distinguished as a compound of definite radicals, 
but merely as conforming to a certain general formula, and the 
only specific character is the atomic ratio between the several 
composite radicals of which the mineral may be supposed to 
consist (214). Thus the composition of common Garnet may 
in general be represented by the formula 

zi vi iy 

J? 8 ,[\ff 2 ] xii O n ^Si 3l 

1 We have reason to hope that a more accurate knowledge of the laws which 
govern the molecular volume of compounds in the solid condition may here- 
after supply this deficiency. 



§ 400.] SILICON. 449 



ii 



VI 



but It may be either Ca, Mg, Fe, Mn, or Or, and [72J either 
\_AL~], [Fe] 2 , or [0 2 ]» a "d garnets have been analyzed in which 
these several radicals are mixed together in every conceivable 
way consistent with the general formula, to which they all con- 
form. T 'his formula, however, is merely the expression of a defi- 
nite ratio between the atomicities of the several classes of radicals 
taken as a whole, and in the last analysis this ratio is itself the 
specific character. Hence the great importance of the atomic 
ratio in mineralogy, and we have already seen how easily it 
can be calculated when the symbol of the mineral is given 
(Probs. 58 and 95, pages 394 and 397). On the other hand, 
from the ratio we can as easily construct the general formula of 
the mineral. Thus in the case of garnet the ratio between the 
dyad, hexad, and tetrad radicals is 6 : 6 : 12, or 1 : 1 : 2, which 
is evidently expressed in its simplest terms by the symbol above. 
In works on mineralogy the atomic ratio is given for each of 
the native silicates, and in any case this ratio is easily deduced 
from the results of analysis by simply extending the method for 
finding the symbol of a body who-e molecular weight is un- 
known (page 43). Having obtained the several quotients which 
represent the relative number of atoms on the supposition that 
the molecular weight is 100, we next multiply each of these 
quotients by the quantivalence of the respective radical-. Last- 
ly, we add together these products for each class of replacing 
radicals, and compare the several sums thus obtained. For ex- 
ample, an actual analysis of the Bohemian Garnet (Pyrope) 
gave the following results: — 



Si 


19.30 


or 


Si0 2 


41.35 


L^y 


11.92 


a 


Al 2 O s 


22.35 


Fe 


7.73 


ti 


FeO 


9.94 


Mn 


2.01 


a 


MaO 


2.59 


Mg 


9.00 


it 


MgO 


15.00 


Ca 


3.77 


u 


. CaO 


5.29 


Cr 


3.19 


a 


CrO 


4.17 





43.77 









100.G9 100.69 

Dividing now each per cent by the atomic weight of the radical, 
and multiplying by its quantivalence, we obtain the following 
numbers : — 

cc 



450 


SILICOX. 




Si 


(19.30 -5- 28 ) X 4 = 2.76 


2.76 


[AI.J (11.92 + 54.8) X 6= 1.31 


1.31 


Fe 


( 7.73 -r 56 ) X 2 = 0.27 




Ma 


( 2.01 -r- 55 ) X 2 = 0.07 




Mg 


( 9.00 -r 24 ) X 2 - 0.75 




Ca 


( 3.77 -f- 40 ) X 2 = 0.19 




Cr 


( 3.19 ~ 52.2) X 2 = 0.12 


1.40 


whence we 


deduce the ratio, 

1.40 : 1.31 : 2.76 or 1:1:2 neai 


•ly. 



[§400 



This ratio, although not exact, is as near the theory as we can 
expect, considering the material and methods used, and is as 
near as we usually obtain. 

There is an uncertainty in the results of all calculations of 
this kind, which arises from the fact that we have no sure guide 
in selecting the radicals to be grouped together. Although it 
is true in general that replacements are limited to radicals of 
the same atomicity, yet most mineralogists admit that radicals 
of the form [i? 2 ]= mav replace 3i?=, and some go so far as to 
reckon a part of the Si among the basic radicals. Hence our 
results are to a certain extent arbitrary, and in many cases give 
no satisfactory information as to the constitution of the mineral 
analyzed ; but by deducing the atomic ratio according to the rule 
just given, we in all instances reduce the results, as it were, to 
the simplest terms, and bring them into a form in which they 
can be most conveniently compared with each other. 

It is usual in works on mineralogy to present the results of 
analysis on the old dualistic plan, as if the mineral were formed 
by the union of various ba-ic anhydrides with silicon. Starting 
with such data it is not, however, necessary to calculate the per 
cent of each radical in the assumed anhydrides before applying 
the above rule, because obviously by dividing the per cent of 
each anhydride by its molecular weight we shall obtain the same 
quotients as before. For example, in the analysis garnet cited 
above, where the data are snven in both forms, we have 



2S fiO 



Si : Si0 2 = 19.30 : 41.35 or 19.30 -*- 28 = 41.35 -f- 60, 

and so for each of the other values. 

In the symbols of the silicates as formerly written on the du- 



§402.] • SILICON. 451 

alistic theory, the atoms of oxygen were necessarily apportioned 
among the different radicals in proportion to their quantivalence, 
although this fundamental distinction between them was itself 
overlooked. Thus the general symbol of garnet would be writ- 
ten, duuLstically, 

3EO,E 2 3 ,3Si0 2 , 

and it is evident that the number of oxygen atoms is in each 
case a measure of the relative atomicities of the radicals with 
which they are associated. Hence the atomic ratio might also 
be found by comparing together the quantities of oxygen which 
the several assumed oxides contain, and this is the manner in 
which the calculation has generally been made hitherto. Hence, 
also, the atomic ratio has been called the oxygen ratio, and was 
long used in mineralogy before its true meaning was understood. 
But although the old method gives the fame results as the new, 
it is not in harmony with our modern theories, and is practically 
less simple. Moreover, the principle is far more general than 
the old method would imply, and may be used with all clas-es 
of compounds as well as with those in which the radicals are 
cemented together by oxygen. Furthermore, it is sometimes 
useful to compare the atomic ratios of the complex radicals 
which may be assumed to exist in different minerals, and inter- 
esting relations may frequently be discovered in this way which 
the old method would entirely overlook. This has already ap- 
peared in solving the problems under aluminum, and requires 
no further illustration. 

401. Silicic Sulphide. SiS 2 .— When the vapor of CS 2 is 
passed over a mixture of silica and carbon intensely ignited, 
this compound is deposited in the colder part of the tube in 
"long, white, silky, flexible, asbestiform needles." It can be 
volatilized in a current of dry gas ; but in contact with moist air, 
or when heated in aqueous vapor, it rapidly decomposes, the 
products being W. 2 & and amorphous silica, the latter of which 
retains the form of the sulphide. It undergoes a similar de- 
composition in contact with liquid water, but the silica formed 
dissolves completely, and the solution, when concentrated, yields 
the same singular vitreous hydrate, resembling opal, described 
above. 

402. Silicic Fluoride, SiF^ is a colorless gas (Sp. Gr. = 52) 



452 SILICON • [§403. 

■which can only be reduced to the liquid state by great pressure 
and cold. It ij easily prepared by the reaction 

(S/O, + 2 CaF 2 + 2II 2 S0 4 ) £s 

2(CaSO, . H*0) -f ©il? 4 . [357] 

When brought in contact with the air it is at once decomposed 
by aqueous vapor and forms dense fumes. Passed into water 
it is absorbed in large quantities, and the products are silicic 
hydrate and hydro-silicic fluoride. 

{SSiF* + m 2 G + Aq) = 

H^0 4 =Si + 2(2HF. SiF 4 + Aq). [358] 

The same solution can also be obtained by dissolving silica in 
hydrofluoric acid. It forms, when saturated, a very sour, fum- 
ing liquid, which evaporates at 40° in a platinum vessel without 
leaving any residue. Hence a very simple way of testing the 
purity of silica. 

The solution of hydro-silicic fluoride acts as a strong acid. 
It dissolves iron or zinc with the evolution of hydrogen, and 
decomposes many metallic oxides, hydrates, and carbonates, 
forming definite salts. It is therefore frequently called silico- 
fluoric acid {H.fSlF b ), and its salts are named silico-fluorides. 
The pota-sium salt, KfSiF Q , and the barium salt, Ba-SiF G , are 
both sparingly soluble in water, and may, therefore, be readily 
obtained by precipitation. Moreover, since the corresponding 
sodium and strontium salts are much more soluble, this reagent 
may be used to distinguish potassium from sodium, but more 
especially barium from strontium. Several of the silico-fluor- 
ides may be readily crystallized. 

Ammonic silico-fluoride (NH 4 ) 2 ^SiF & . xH.,0, 

Cupric silico-fluoride Cu-SiF Q . 7H 2 0, 

Manganous silico-fluoride Mn=SiF 6 . 1 H. z O. 

403. Silicic Chloride, SiCl 4 , is formed by passing a current 
of chlorine gas through an intimate mixture of silica and car- 
bon heated intensely in a porcelain tube. 

Sj0 2 + Co + 201-01 = 20® + mm 4 . [359] 

It is a colorless, volatile liquid (Sp. Gr. 1.52), boiling at 50°, 



§40G.] SILICON. 453 

and is decomposed by water into hydrochloric acid and silicic 
hydrate. Gp, (&t. of vapor 5.94. It is also slowly decomposed 
by H,S. 

Si CI, 4- H 2 S = Si Cl 3 ,Hs + HCl [3 GO] 

The new product is a colorless liquid, boiling at 9G°, and yield- 
ing a vapor whose Sp. (St. = 5.78. 

When the vapor of Si CI, is pas;-ed through a white-hot por- 
celain tube it undergoes a partial oxidation, and is in part con- 
verted into an oxycliloride, 

2SiCli + = SUOCl, + ®K31, [361] 

the oxygen required coming from the glazing of the tube. This 
compound is also a colorless fuming liquid, resembling the chlo- 
ride. It boils at 138°, and has Sp. (St. = 10.05. 

404. Silicic Bromide, SiBr„ may be formed in a similar 
way, and closely resembles the chloride, but is less volatile, 
boiling at 153°, and crystallizing at from 12° to 15°. Sp. (5r. 
of vapor 12.05. The compound SiCl 3 ,I, Sp. (&X. == 7.25, is 
also known. 

405. Silicic Iodide, SiT„ is a colorless crystalline solid, melt- 
ing at 120°. 5, and boiling at about 290°. £p. (£)r. of vapor 
19.12. It crystallizes in regular octahedrons, and is obtained 
by passing iodine vapor in a stream of C0 2 over ignited silicon. 

40G. Silicic Hydride. Sill,. — One of the silicic ethers (409), 
when heated with sodium, furnishes this remarkable compound 
in a pure condition. 

HiO&)?Q?SiE) = H(C 2 H 6 )fO;=Si) + mm,. [3G2] 

The sodium induces the chemical change by its mere presence. 
The composition of silicic hydride has been determined by the 
following reaction : — 

mm, + (2K-o-n+ mo-\- Aq) = 

(K 2 =0 2 =SiO -f Aq) + Am-m. [3G3] 

It is a colorless gas which inflames at a very low temperature 
(under some conditions spontaneously), and yields when burnt 
silicic anhydride and water. 



454 



SILICON. 



[§407. 



407. Silicic Hydrochloride, SiHCl 3 , is a colorless inflamma- 
ble liquid, obtained by passing HCl over ignited silicon. It 
has Sp. (Br. == 4.64, and may be regarded as the chloride of 
the radical (SiU) = Cl 3 , corre.-pouding to chloroform (CN) = Cl 3 > 
among the compounds of carbon. The corresponding bromine 
and iodine compounds are also known. When mixed with 
water these substances are decomposed, and a voluminous white 
powder is formed which has been called leukon. 

2SiIICl 3 + 3R 2 = (SiOB).fO -f GBCL [364] 

Leukon dissolves in the alkaline hydrates or carbonates, yield- 
ing an alkaline silicate and evolving hydrogen. It al.-o decom- 
poses water, and acts in general as a re lucing agent. 

408. Silicic Ethide, St(0 2 H 6 )t, and S» tide Meth de, Si( CH 3 ) 4 
are two colorless volatile liquids, prepared by heating St CY 4 
with zinc ethide and zinc methide in sealed tubes. They 
boil respectively at 30° and 153°, and their vapors have a 
6p. (J5r. of 3.08 and 5.13. Also another compound has been 
described whose symbol may be written 0=Sii(C. 2 H 5 )Q. 

409. Silicates of the Organic Radicals or Silicic Ethers. — 
A large number of these compounds have been prepared, con- 
taining the radicals methyl, ethyl, and amyl, either singly or 
associated in different combinations. They are all colorless 
volatile liquids, highly combustible, and having for the most 
part an ethereal odor. We give in the following table the 
symbols, the boiling-points, and the vapor-densities of several 
of the most interesting ethers, and of the chlorhydrines (349) 
derived from them. 





Sp. Gr. 
of Liquid. 


Boiling-point. 


Vapor-density. 


Obs. 


Calc. 


(CB s )f0 4 =Si 


1.059 


121°-122° 


5.38 


5.26 


(C II s )£OfSi- CI 


1.195 


114°.5-115° 


5.58 


5.42 


(C H 3 ) 2 =0fSi=Cl 2 


1.259 


98°- 103° 


5.66 


5.57 


(Cff s )-0-Si=-Cl s 




82° -86° 


5.66 


5.73 


(c u 3 )<MO b iS; 2 o 


1.144 


201°-202°.5 


9.19 


8.93 


(C 2 H 5 )mSi 


0.968 


165° -166° 


7.32 


7.27 . 



§409.] 



SILICON. 



455 





Sp. Gr. 

of Liquid. 


Boiling-point. 


Vapor-density. 


Obs. 


Calc. 


(C\H 5 )f0.fSi-H 




134° 




5.68 


{C 2 H 5 ).fOfS r Cl 


1.048 


157° 


7.05 


6.81 


(CJh)rOrSi-Cl 2 


1.44 


137° 


6.76 


6.54 


(C 2 B 5 )-0-Si-=t% 


1.291 


104° 


6.38 


6.22 


{C 2 H 5 \W ( m*0 


1.020 




12.02 


11.86 


{C\H^{CM,Oy-OiSl 




190° 




7.69 


(0 ll z %{C,H 5 )iO£Si 


1.004 


143° -146° 


6.18 


6.23 


(CHz),(C,H 5 )f(JfSi 


0.981 


155°-157° 




6.72 


(CJh)»(C 5 H n )m& 


0.915 


245° -250° 




10.12 


(C 2 U 5 ), {C 5 H u ) 3 WfSi 


0.913 


280° -285° 




11.57 



The following equations illustrate some of the reactions by 
which these compounds have been prepared: — 

AC. 2 H f O-H+ SiCk =: (C 2 H s )£0£Si + AHCl [365] 

2((C 2 H 5 )fOi-Si) + SiCk = ±(C 2 H 5 )iOfSiCl [366] 

{C 2 H b )fOiSi + SiCl A == 2{C 2 H 5 ),r0.rSlCL [367] 

( 2 H 5 )i Of Si CI + C b H n -0-H= 

(C 2 H 5 )s,(C 5 ff n )lOi-Si-\-HCl [368] 

S(C 2 Il 5 )-0-H+ SiHCl 3 = (C 2 H^OiSiB r + SIICL [369] 

§(C 2 H 6 )-0-H-\- SuOCk = (C 2 H 5 )gQiSi 2 +6 HCl [370] 

In general, these reactions may be obtained by simply heat- 
ing together the several factors, enclosed if necessary in sealed 
tubes. The process is usually complicated by accessory changes, 
and a mixed product results, which must be purified by repeated 
fractional distillation. 



456 



QUESTIONS AND PROBLEMS. 



Questions and Problems. 

1. Compare the properties of silicon in its different conditions with 
those of boron. 

2. Make a table illustrating the relations of the possible hydrates 
of silicon. 

3. Required the general formula of the following mineral species 
whose atomic ratios are given in the table : — 





i 

R 


II 
R 


VI 


Si 


H 


Anorthite 




1 


3 


4 




Sarcolite 




1 


1 


2 




Epidote 




1 


2 


3 




Vesuvianite 




3 


2 


5 




Leucite 


1 




3 


8 




Beryl 




1 


1 


4 




Iolite 




1 


3 


5 




Oligoclase 


1 




3 


10 




Natrolite 


1 




3 


6 


2 


Analcime 


1 




3 


8 


2 


Harmotome 




1 


3 


10 


5 


Stilbite 




1 


3 


12 


6 



Formula required. 



}).[R 2 ] iii(9 8 viH^ 2 

IT 

7? 2 .[/? 2 >iii0 8 viiiS; 4 4 

ii 3L Jj u a 6 

^2' L # 2 ]s Xvi ^16 XV ' % 2 

Kl^y^O s ymSl 3 2 .2FI 2 
2? 9 ,[J? 2 ]yiii0 8 viii^0 4 .2H a O 

^,[/? 2 ]viiiO fe vni^.(9 6 .5// 2 

ig,[Jg 2 ]viiiQ 8 vi»5i 6 Q 8 . 6/7,0 



The number of atoms of oxygen, which form the vinculum in each 
of the above formulas, is always necessarily equal to the total atom- 
icity of all the basic radicals, and as many atoms of oxygen are asso- 
ciated with the acid radical as are required to complete the molecule. 
The la-t evidently serve to bind together the atoms of silicon when 
they are in excess over the number required to neutral'ze the base 
(151). The precise form we give to the symbols is in great meas- 
ure arbitrary, and must be determined from many circumstances, 
which do not influence the results of analysis; and the great advan- 
tage of expressing these results in the form of an atomic ratio is found 
in the fact that they are thus reduced to the simplest terms, and ex- 
hibited independently of all hypothesis, leaving each student to con- 
struct the formulas according to his own theoretical conceptions. 



QUESTIONS AND PROBLEMS. 



457 



4. Represent the constitution of Anorthite, Sarcolite, and Beryl 
by graphic symbols. 

5. In the following table the percentage composition of a number 
of native silicates is given on the usual plan, as it they were composed 
of basic anhydrides and silica. It is required in each case to deduce 
the atomic ratio and construct the formula. 





Na 2 


K 2 


Li 2 


1 
FeO CaO 

1 


M S 


Al 2 O z 


Fe 2 3 


Si0 2 


H 2 


Ratio. 


TTollastonite 








48 3 








517 




1:2 


Pyroxene 








8.0 24.9 


13.4 






53 7 




1:2 


Spodumene 






6.4 








29.4 




64 2 




1:2 


Petalite 


1.2 




3.3 








17.8 




77.7 




1:4 


Forsterite 












5714 






42.86 




1:1 


Iron-Garnet 










17 3 


124 




331 


37.2 




1:1:2 


Zoisite 










37 3 




22 8 


39.9 




1:2:3 


Ilvaite 








31.5 12.3 






23.4 32 8 




3:2:5 


Sarcolite 


4.1 








334 




22.8 


'39.7 




1:1:2 


Andesine 


6.53 


1.08 






5.77 


1.08 


24 28 


1.58 59 60 




1:3:8 


Analcime 


14.1 












23.3 


54.4 


8.2 


1:3:8:2 


Heulandite 










9.2 




18.9 




59.1 


14.8 


1 : 3 : 12 : 5 



6. It was formerly supposed that the symbol of silica was Sifi^ 
corresponding to that of boric acid, B 2 3 , when Si— 21 and O = 16. 
What facts can you adduce in. support of the symbol adopted in this 
book? 

7. Deduce the atomic weight of silicon from the data of (409) ac- 
cording to the principle of (19). It is assumed that the percentage 
composition of the various compounds has been accurately determined 
by analysis. 

8. Point out the analogies between the properties of silicic fluoride 
and chloride, and those of the corresponding compounds of boron. 

9. Compare the chemical qualities of sileon with those of the 
elements immediately preceding it in our classification. To which 
element is it more closely allied? 

10. Compare the chemical qualities of silicon with those of carbon, 
and illustrate by examples the analogies between thos^ elements. 

11. Point out the examples of chlorhydrines in the table of (409). 

12. Describe and illustrate by reactions the methods by which the 
silicic ethers and chlorhydrines are prepared. 



20 



458 CAEBON. [§410. 



Division XXL 

410. CARBON. C= 12. — Tetrad. One of the most 
widely diffused, and one of the most important elements in the 
scheme of* terrestrial nature. United to the three aeriform ele- 
ments, oxygen, hydrogen, and nitrogen, it forms the chief solid 
substratum of all organized structures. Combined with oxygen 
it forms the carbonic anhydride of the atmosphere, which is the 
food of ihe whole vegetable world. In a nearly pure condition, 
or combined with hydrogen, it is found in the strata, forming 
those deposits of coal and petroleum which are such great stores 
of light, heat, and motive power (64). Lastly, it is an essential 
constituent of the limestones and Dolomites, which constitute 
an important part of the rocky crust of the globe (279) (312). 
The elementary substance is found in nature in three very dif- 
ferent conditions, namely, coal, graphite, and diamond. 

411. Coal. — Ail organized tissues, and many other carbo- 
naceous materials, when heated without free access of air, are 
charred; that is, the volatile ingredients are driven off, and more 
or less of the carbon is left behind in an uncombined condition. 
Common charcoal, animal charcoal, lamp-black, ivory -black, £;c. 
are all artificial products of this kind, and mineral coal is the 
charred remains of the rank vegetation of an early geological 
epoch. Since carbon is, under all circumstances, infusible and 
non-volatile, coal frequently retains the structure of the organic 
tissue from which it was derived, and this element may therefore 
be regarded as the skeleton of all organic forms, which in the 
process of growth gather around this solid nucleus the elements 
of air and water. The great porosity of many kinds of coal, 
which results from its organic structure, renders it a powerful 
absorbent both of aeriform and liquid materials, and hence the 
use of wood-charcoal as a disinfecting, and of bone-black as a 
decolorizing, agent. The ready combustibility of coal is, how- 
ever, the most characteristic and important, as it is the most 
familiar, quality of this variety of carbon, which is peculiarly 
adapted for its all-important uses as fuel, not only on account of 
its high calorific power, but also because it retains its solid con- 
dition at the highest furnace heat, and because the product of 
its combustion is an invisible innocuous gas, the appropriate 



§413.] CARBON. 459 

food of the plant. In its more porous conditions coal is a non- 
conductor of heat and electricity, has a low specific gravity and 
a high specific heat, both varying, however, in different varieties 
between quite wide limits. 

412. Graphite has usually a foliated structure, and is found 
occasionally in small six-sided tables belonging to the third sys- 
tem, but it is also met with in compact amorphous masses. From 
its frequent association with crystalline minerals, evidently the 
products of aqueous action, we naturally infer that it must have 
been formed in a similar way; but the nature of the process is 
not understood. Graphite is very soft, leaving a black shining 
streak o;i paper, and has a Sp. Gr. = 1.209. It is practically 
incombustible, ahhough it burns slowly in an oxyhydrogen flume. 
It has a metallic lustre, and, since it also conducts electricity 
nearly as well as the metals, it has been called metallic carbon. 

The carbon which separates from some varieties of cast-iron 
when the molten metal slowly cools is in the condition of graph- 
ite, and the cavities in iron slags are sometimes lined with crys- 
talline plates of the same material. Moreover, when coal is 
intensely heated in a close vessel, it acquires the characteristic 
lustre and conducting power of the same mineral, and a similar 
product is formed in the iron retorts in which illuminating gas 
is manufactured. Ordinary coke also sometimes approaches the 
same condition, but ail these materials are very hard, and thus 
differ from true graphite. 

Graphite may be obtained in a state of minute sub-division 
by heating with strong sulphuric acid the coarsely pulverized 
mineral, previously mixed with one fourteenth of its weight of 
potassic chlorate, and, after washing with water and drying, 
igniting the residue. If this process is many times repeated 
the graphite is converted into a yellow crystalline product which 
has been called graphitic acid, and which has been regarded as 
a peculiar compound of the graphitoidal condition of carbon. 
Analysis gives the symbol C n lf 4 5 . 

413. Diamond. — This well-known gem is also a crystalline 
condition of carbon. It affects the forms of the monometric 
system, and may be cleaved in directions which are parallel to 
the faces of the regular octahedron. Its peculiar brilliancy is 
due to a very high refractive and dispersive power united to a 
strong lustre called adamantine. The effect is greatly increased 



460 CAKBON. [§ 413. 

by the lapidary, who cuts numerous facets on the gem, which 
reflect and disperse the light in various directions. Diamond 
is the hardest substance known, and can therefore only be cut 
with its own powder. Opaque stones called "black diamonds," 
which are otherwise valueless, are pounded up and used tor this 
purpo.-e. On account of its great hardness the diamond is also 
used for cutting glass, and the convex faces of the crystals en- 
able them to bear the necessary pressure without breaking. 
The diamond burns at a high temperature much more readily 
than graphite, and in an atmosphere of pure oxygen sustains its 
own combustion, yielding C0. 2 like all other forms of carbon. 
It is a poor conductor of electricity, but when intensely heated 
in the voltaic arc it suddenly acquires this power, becomes spe- 
cifically lighter, and is converted into a kind of coke. The dia- 
mond has never been made artificially, and we have no knowl- 
edge as to its origin. It is found in alluvial soil at only a few 
localities, chiefly in India, Borneo, and Brazil. 

It will thus be seen that carbon presents the most remarkable 
example of allotropism which has been observed in nature, and 
the essential differences between the three states appear chiefly 
in the form, density, and capacity for heat, which we sum up in 
the table below : — 





Crystalline Form. 


Sp. Gr. 


Sp Heat. 


Wood Charcoal 


Amorphous 


0.800 


0.2415 


Graphite 


Hexagonal 


2.800 


0.2027 


Diamond 


Isometric 


3.500 


0.1469 



In all these forms carbon is chemically the same, and yields 
the same product (O0 2 ) when burnt. It is not only non-vola- 
tile and infusible, but does not even soften in the hottest fire; 
although in the experiments of Despretz, with a voltaic battery 
of intense energy, it appears to have undergone incipient fusion, 
and to have been partially volatilized. Lastly, although com- 
bustible at a high temperature, yet under ordinary conditions 
carbon effectually resists, and for an indefinite period, the action 
of all atmospheric agents, and its uses for fuel on the one hand, 
and for printing-ink on the other, are remarkable illustrations of 
the singular twofold aspects of this element in the economy of 
nature. 



§414.] CARBON AND OXYGEN. 401 

CARBON AND OXYGEN, OR SULPHUR. 

414. Carbonic Anhydride. C0. 2 . — With this aeriform pro- 
duct of ordinary combustion the student must have already be- 
come familiar. Although a gas under ordinary conditions, it can 
be condensed by pressure and cold to a colorless limpid liquid, 
which freezes by its own evaporation to a light flocculent solid, 
outwardly resembling snow, a condition in which it is used to 
produce a great degree of cold. As a gas it is distinguished by 
the absence of all those qualities which affect the senses, and 
hence, although playing such an important part in nature, it es- 
caped notice until the year 1757, when it was first dk-covered 
by Dr. Black. It is not only a product of the combustion of 
all carbonaceous materials, and of the slow oxidation of organic 
tissues called decay, but it is also one of the chief products of 
respiration, and of the other processes of animal life. Carbonic 
anhydride is likewise formed during fermentation, and is the 
cause of the effervescence in all fermented l'quids. It is a pro- 
duct of volcanic action, and is copiously evolved from the earth 
in many localities, especially in volcanic districts. As it is much 
heavier than the air, Gp. (6>r. = 1.529, it not unfrequently col- 
lects in wells, mines, and caverns, and it is the choke-damp which 
has occasioned so many serious accidents ; for, although not, 
properly speaking, poisonous, the free secretion of carbonic an- 
hydride from the body is an essential condition of life, and this 
is arrested as soon as the amount in the atmosphere exceeds a 
few per cent. Hence also the necessity of ventilating crowded 
apartments. 

Although an immense flood of carbonic anhydride is being 
constantly poured into the atmosphere from the various sources 
just enumerated, yet in the beautiful balance of creation the 
plant restores the equilibrium which these causes tend to dis- 
turb. This product of animal life, of decay, and of combustion 
is the food of the vegetable world, and, as has been stated (G4), 
the sun's rays acting on the leaves of the plant undo the work of 
destruction, and while the plant fixes the carbon in its tissues, 
the oxygen is restored to the atmosphere. While the plant is 
an apparatus of reduction, the animal is an apparatus of com- 
bustion, in which the carbon it receives with its food is burnt 
in each act of life, and every breath carries back carbonic an- 



462 CARBON AND OXYGEN. [§415. 

hydride to the atmosphere, ready to be reabsorbed by the plant, 
and repass through the phases of organic life. 

Water dissolves very nearly its own volume of carbonic 
anhydride gas (53), and this important agent is as universally 
diffused through the waters of the globe as it is through the 
atmosphere, and sustains the same intimate relations to the 
plants and animals which inhabit the water as it does to those 
which live in the air. Moreover, in this condition of solution 
carbonic anhydride is a very active and important agent in the 
mineral kingdom, exerting a powerful solvent action on many 
minerals which would be otherwise unaffected by water, and 
thus causing extensive geological changes. (279), (312), and 
Prob. 67, page 394. 

Although the solution of C0 2 in water acts in all respects 
like a simple solution (54), yet there are reasons for regarding 
it as a solution of carbonic acid, and writing its symbol thus, 
(H.fO.fCO -\- Aq). It has an acid reaction (39), and dissolves 
iron with the evolution of hydrogen gas (335). Moreover, it 
neutralizes many basic hydrates, and such reactions are most 
simply regarded as examples of direct metathesis, thus: — 

(Ca-OfH 2 + H 2 =OfCO + Aq) = 

Ca = 2 =CO + (2H 2 + Aq). [371] 

Carbonic acid is a weak dibasic acid, and forms two distinct 
classes of salts, the most important of which have already been 
described (123), (124), &c, and, as may be inferred from what 
has been said, carbon is next to silicon the most abundant acid 
radical in the mineral kingdom. 

The quantity of C0 2 formed by the burning of a known 
weight of carbon can be collected and weighed with the greatest 
accuracy, and it was thus that the atomic weight of carbon was 
determined. Dumas found in a series of very accurate experi- 
ments that 100 parts of pure carbon yield exactly 366.66 + parts 
of C0 2 . 

415. Carbonic Oxide, CO, is, like C0 2 , a colorless gas, but 
contains in the same volume only one half as much oxygen, and 
its molecules not being saturated, act as powerful dyad radicals 
(69). The gas is devoid of odor or taste, is very poisonous, is 
but slightly soluble in water, and has never been condensed to 
the liquid state. When ignited it burns with a blue flame, and 



§415.] CARBON AND OXYGEN. 463 

when in contact with heated metallic oxides it acts as a power- 
ful reducing agent, in each case eagerly absorbing more oxygen 
without changing its volume. It is formed abundantly in all 
furnaces and grates whenever the first product of combustion, 
always C0 2 , subsequently passes through a mass of ignited car- 
bonaceous combustible, and it plays au important part in many 
metallurgical processes, not unfrequently occasioning a great 
loss of heat by escaping combustion. It is also formed when 
steam is passed over ignited coal, and it is a chief ingredient in 
the so-called water gas. 

Carbonic oxide may be obtained in a pure condition by a 
number of chemical reactions, of which the ioliowiug is the 
most available : — 

Ki{FeC Q N b ) + GJI 2 =0.fS0 2 + GH,0 = 

Potassic Fe.rocyunide. 

Fe-0,=SO, + 2K 2 =0 2 =Sa 2 + 3(NffJfOfSO a -f- G@®. [S72] 

So, also, when oxalic acid is dehydrated, — best by heating the 
crystals with concentrated sulphuric acid, — it breaks up into 
C0 2 and CO, which are evolved in equal volumes, and the CO 
may be isolated by passing the gas through a solution of caustic 
alkali which absorbs the C0 2 . 

H 2 = Of C 2 2 — R 2 = 0® 2 + O®. [373] 

In theoretical chemistry CO is chiefly interesting as an im- 
portant acid radical, and when acting in this capacity it is usu- 
ally known as carbonyl. It is the acid radical not only in the 
normal carbonates, but also in almost all of the organic acids. 
The following beautiful synthetical reaction, obtained by simply 
heating carbonic oxide gas with potassic hydrate, illustrates the 
relations of this radical to an important class of organic acids. 

K-0-H+ CO = K-0-{CO-H). [374] 

Potassic Formate. 

Under the influence of direct sunlight, carbonic oxide combines 
directly with chlorine, forming CO=Cl 2 , called phosgene gas. 
This compound is at once decomposed both by water and am- 
monia {NH^), and in each of the resulting reactions the radical 
CO evidently retains its integrity. 

CO- Cl 2 + H 2 = 2HCI + CO* [375] 

CO = Cl 2 + ±H,N = H 2 ,KfNf CO + 2NH, Cl. [376] 

Urea. 



464 CARBON AND OXYGEN. [§416. 

41 6. Oxalic Acid. H. r Of C, 2 . 2H 2 0. — The anhydride 
of this acid, C. A 0& has never been obtained, and the acid itself 
forms the first term of an important series of compounds, all of 
which contain hydrogen. Strictly, therefore, it cannot be classed 
with the Simple compounds of carbon and oxygen, but neverthe- 
less it is best studied in this connection. 

The calcic and potassic salts of oxalic acid are found imthe 
juices of many plants, and when organic bodies are oxidized by 
nitric acid or similar agents, this acid is one of the most com- 
mon products. It is made in the arts by the action of nitric 
acid on sugar or starch, and also by heating sawdust with caustic 
potash. 

Oxalic acid easily crystallizes in prisms which have the com- 
position indicated above. These crystals lose their water of 
crystallization at 100°, and at 160° the body it>elf is broken 
up, the products being carbonic anhydride and formic acid ; 
but the greater part of the last is still further decomposed into 
water and carbonic oxide, and a portion of the oxalic acid al- 
ways sublimes unchanged. 

C 2 H 2 0, — CH 2 2 + C0 2 and CH 2 2 = H 2 + CO. [377] 

When, however, the acid is heated with glycerine, ihe reaction 
is arrested at the first stage, and yields the equivalent quantity 
of formic acid. 

Oxalic acid is both diatomic and dibasic. Thus we have 

Normal Potassic Oxalate X 2 =0 2 =C 2 2 . H 2 0, 

Acid Potassic Oxalate (Salt of Sorrel) H,K-OfC 2 2 . H 2 0, 
Super-acid Potassic Oxalate H,K=0 2 -C 2 2 . Hf0 2 -C 2 2 . 2H 2 0. 

The last is usually regarded as a molecular compound. With 
the exception of the alkaline salts, the oxalates are, as a rule, 
insoluble or difficultly soluble in water, and on the great insolu- 
bility of calcic oxalate several important analytical processes 
depend. 

Calcic oxalate, when heated, is converted into calcic car- 
bonate. 

Ca-0 2 ~-C 2 2 = Ca-0 2 -CO + CO. [378] 

When, however, the acid itself is heated with an excess of lime, 
we obtain a somewhat different result. 

R f 2 -C 2 2 -\-2CaOz=2Ca-0 2 -CO-\-H-H. [379] 



§416.] CARBON AND OXYGEN. 465 

Oxidizing agents convert oxalic acid into C0 2 (Prob. 18, 
page 391) by removing the typical hydrogen. 

H 2 =0 2 =C 2 2 +0 = 11,0 + 2C0 2 . [380] 

Substances having a strong attraction for water transform 
the acid into CO., and CO [373]. 

Argentic oxalate, when heated, is resolved with explosion 
into metallic silver and C0 2 . 

Ag 2 --0 2 =C 2 2 = Ag-Ag + 2 C0 2 . [381] 

On the other hand, when an amnlgam of potassium is heated 
in an atmo-phere of C0 2 , the gas is absorbed and potaj>sic ox- 
alate results. 

K-K +2CO a = K/ Or C 2 0, [382] 

These reactions all justify the rational symbol assigned to ox- 
alic acid, *md by writing the symbol as in the mar- 
gin the relation of the atoms is made more evident. H-U-C = U 
We thus see that dry oxalic acid may be regarded H~0~C^O 
as formed by the union of two atoms of the com- 
pound radical {Ho- CO)-, he'd together by one affinity of each 
of the carbon radicals, which, when not thus satisfied, may join 
the radical to any other group of atoms that is in the condition 
to hold it. This radical is called oxatyl, and dry oxalic acid is 
evidently the corresponding radical substance. Oxatyl, as is 
evident, is not only univalent, but also monobasic, and therefore 
must transform any group of atoms to which it is united into 
an acid. Moreover, the basicity of such an acid will be meas- 
ured by the number of atoms of oxatyl which it contains. Now 
nearly till the so-called organic acids may be regarded as com- 
pounds of oxatyl with the different hydrocarbon radicals. 
Those containing one atom of oxatyl are monobasic, those con- 
taining two atoms are dibasic, those containing three are triba- 
sic. Oxatyl, however, must itself be regarded as a compound 
of carbonyl with hydroxl, and thus we arrive at this important 
general principle. The basicity of an organic acid is determined 
by the number of atoms of Ho which it contains associated with 
carbonyl. 1 Moreover, it now appears why the basicity may be 

1 This theory of the constitution of organic acid, which has heen recently 
advanced and abundantly illustrated by Professor Frankland, of London, is one 
20* DD 



4GG CARBON AND NITROGEN. [§417. 

less than the atomicity ; for the last is measured by the total 
number of Ho atoms present, however united to the nucleus of 
the compound (43). But while the hydrogen of all the Ho 
atoms in a compound may be displaced by very positive met- 
als, or compound radicals of either class, we can only displace 
by double decomposition with bases the hydrogen of those atoms 
which are associated with carbonyl. 

The explanation of this important principle seems to be that, 
while a strong positive metal, such as sodium, will, like a pow- 
erful magnetic pole, increase the attraction of the point of affin- 
ity to which it is opposed, and thus give to it an energy it 
would not otherwise possess, yet in the ordinary metathetical 
reactions the atoms of hydrogen cannot be displaced unless they 
are in a polar condition, such as is determined by their associ- 
ation with carbonyl. 

417. Carbonic Sulphide. CS 2 . — Charcoal burns in an at- 
mosphere of sulphur vapor with almost as much energy as in 
oxygen, forming a colorless gas, which at the ordinary temper- 
ature of the air condenses to a very volatile liquid, distinguished 
for its very great refractive and dispersive power, and much 
used in the arts as a solvent of phosphorus, sulphur, and caout- 
chouc. The compound CS has never been obtained in a free 
state, but the following reactions indicate that it exists as an 
acid radical in certain sulphur salts (38). 

K 2 S + CS 2 == KfSf CS. [383] 

(Pb=0.f(N0 2 ) 2 + KfSfCS -f Aq) = 

Pb=S.fCS+ (2K-0-JST0 2 + Aq). [384] 

Pb=S 2 =CS + (H 2 S+ Aq) = PbS-\- (H 2 =S 2 =CS + Aq). [385] 



CARBON AND NITROGEN. 

418. Cyanogen. CN. — Although carbon will not combine 
directly with nitrogen, yet when heated in an atmosphere of 
this gas, and in the presence of a strong alkaline base, the two 
elements unite with the alkaline metals, and the resulting pro- 
of the most important contributions recently made to Chemistry, and the au- 
thor would here acknowledge his great indebtedness to the papers of this emi- 
nent chemist in the preparation of the present division of this work. 



§419.] CARBON AND NITROGEN. 467 

duct contains the compound radical CN, with which the stu- 
dent is already familiar, under the name of cyanogen. 

KfOfCO + 4(7+ N=-N = 2K-CN+ SCO. [386] 

Like carbonyl, cyanogen is a very strong negative or acid 
radical, and, if we accept the theory of Frankland, we need admit 
no other acid radical than these two " in investigating the whole 
range of organic compounds." 1 In many of its chemical relations 
cyanogen closely resembles the elements of the chlorine group, 
forming many compounds which are analogous to the corre- 
sponding chlorides, bromides, and iodides, but in other respects 
it differs widely from these elements, both on account of its 
compound nature, and the singularly complex relations of the 
two elements of which it consists. Its univalent condition is 
an obvious result ot the atomicities of its two constituents. 

419. Cyanogen Gas, CN-CN or Cy~Cy, bears the same re- 
lation to the radical CN that chlorine gas bears to the element 
chlorine (69), (113). It is easily made by heating mercuric 
cyanide. 

Ug€y 2 = Hg + Oy-%. [387] 

At the same time a brown non-volatile product is formed which 
is called paracyanogen. This body is isomeric with the gas, 
but probably represents a more condensed molecular condition, 
and is converted wholly into cyanogen when heated in an inert 
atmosphere. 

Cyanogen has been condensed to a liquid, boiling at — 20°.7, 
and freezing below — 34°, which is its melting-point. The gas 
is colorless, has a suffocating odor, and is poisonous. It burns 
with a beautiful flame, which recalls the color of peach-blossoms, 
and the products of its combustion are C0 2 and N=N It dis- 
solves in water, but not so freely as in alcohol. The aqueous so- 
lution, moreover, is not permanent, for the cyanogen slowly unites 
with the elements of water, changing into ammonic oxalate. 

CN- CN + 4 77 2 = {NH,) 2 = 2 = C 2 2 . [388] 

1 There is, however, a class of somewhat obscure acids, formed by the action 
of E 2 = 0. 2 =S 6> 2 on various organic substances, in which the radical (IIo-S0 2 )- 
appears to play the same part as the radical oxatyl in the compounds just no- 
ticed. Such bodies were formerly said to be copulated ©r conjugated, and 
these terms, though latterly discarded, were not wholly inappropriate. 



4G8 CAKBON AW N1TK0GEN, [§ 420. 

On the other hand, when amnionic oxalate is heated the action 
is reversed, and these facts show how easily carbonyl and cyan- 
ogen are convertible. Cyanogen unites directly with potassium, 
forming K-QN. 

420. Hydrocyanic Acid, ff^CJST. — The anhydrous acid (a 
combustible and very volatile liquid) is most readily obtained 
by passing II 2 S over HyCy 2 , but a solution of the acid in water 
(the prussic acid of pharmacy) may be made by distilling po- 
tassic cyanide or ferro-cyanide with dilute sulphuric acid. 

Hydrocyanic acid has the peculiar odor of bitter almonds, 
and is intensely poisonous. It is a \ary unstable body, and 
both the hydrous and the anhydrous acid undergo spontaneous 
decomposition, which is greatly accelerated by the action of the 
light. When diluted with water, and mixed with a mineral 
acid, it is more permanent, but it is so volatile that even the 
very dilute acid used in pharmacy rapidly loses strength when 
exposed to the air. 

By absorption of the elements of water both amnionic oxalate 
and amnionic formate are slowly formed in the aqueous acid. 
The first by a reaction similar to [388J, and the second thus, 

H-CN+ 2ff i O = 2MI<-0-(CO-JI). [389] 

Amnionic Formate. 

When the vapor of ammonic formate is passed through a red- 
hot tube, the last reaction is reversed. In like manner, when 
hydrocyanic acid is mixed with hydrochloric acid (both concen- 
trated), we have 

E~Cy+ HCl + 2H 2 = jr-O'(CO-ff) + NH^Cl [390] 

Formic Acid. 

421. Cyanides. — Hydrocyanic acid reddens litmus feebly, 
and potassic cyanide has an alkaline reaction (39). It however 
freely dissolves ffyO, forming JIgCy 2 . and in a similar way (or 
more readily by metathesis from potassic cyanide) a large num- 
ber of metallic cyanides may be obtained. The alkaline cyan- 
ides are very soluble in water, and several of the cyanides of 
the heavier metals, like flgCy 2 , dissolve to a limited extent. 
Most of them, however, are insoluble in pure water, but with 
few exceptions they all dissolve freely in solutions of the alka- 
line cyanides, with which they form double salts, and solutions 
of AgCy and AuCy in (KCy -\- Aq) are very much used in 



§422.] 



CARBON AND NITROGEN. 



469 



the process of electroplating. The double cyanides are a still 
more definite and numerous class of salts than the simple cyan- 
ides. Among them we may cite as examples 

Ay Cy . KCy and Zn Cy 2 . 2 KCy. 

All these cyanides contain cyanogen as such, and, with few 
exceptions, when heated with dilute hydrochloric acid, they 
yield HCy, and, if soluble, are violent poisons. There is, how- 
ever, another class of compounds formed by combining with the 
alkaline cyanides the cyanides of iron, cobalt, chromium, pla- 
tinum, and a few of the rarer metals, which do not evolve 
HCy under the influence of hydrochloric acid, and have not the 
same deadly character. Moreover, the metals which they con- 
tain cannot be displaced by the usual metathetical methods. 
Hence we have come to the conclusion that these bodies are not 
simple cyanides of the metals, but contain far more complex 
radical*, of which the metals just mentioned form a part. The 
most important of these compounds are described in the next 
two sections. 

422. Ferrocyanides. B^(FeC 6 N' (i ) or R^Cfy. — Potassic 
ferrocyanide (yellow prussiate of pota>h), K^Cfy, is an impor- 
tant commercial product, manufactured on a large scale by fus- 
ing nitrogenized animal matter with potassic carbonate and iron- 
filings, lixiviating the resulting mass with water, and crystalliz- 
ing. The salt forms large yellow, square, tabular crystals, is 
very much used in dyeing, and is the primary source of all the 
cyanogen compounds. It may also be made from KCy or HCy 
by the following reactions : — 

FeS + <SK-CN= K^(FeC^) + K 2 S. [391] 

1. 2Fe 2 3 + 3FeO+18H-CN = 

[Fe^FrC^ + 9J7 2 <9. [392] 

Prussian Blue. 

2. in^Q/jf. + (UK-Bo + Ag) = 

2£Fe,yHo, + (ZKfCfy + Ag). [393] 

When fused, the ferrocyanide is partially decomposed, yield- 
ing potassic cyanide, which is made in great quantities in this 

Ki(Fe CyV 6 ) = 4/i- CN + Fe C 2 +N-K [394] 



470 CARBON AND NITROGEN. [§423. 

way. By previously mixing the ferrocyanide with potassic 
carbonate a larger product is obtained, but less pure, as potassic 
cyanate is formed at the same time. 

KHFeOJTt) + KfOfCO = 

5K-Ctf+K-0-C2r+ Fe + CO, [395] 

From the solution of the potassium salt various ferrocyanides 
are easily prepared by simple metathesis, and several of them 
have striking and characteristic colors. Thus, when the solu- 
tion is mixed with hydrochloric acid and ether, hydro-ferrocy- 
anic acid is precipitated. 

iT 4 i Cfy + 4:HCl = Hi Cfy + 4KCL [396] 

"With a ferric salt we obtain Prussian blue (ferric ferrocy- 
anide). 

(2[J^ 2 ]ICT 6 + ZKfCfy + Aq) = 

[/y*»qjfo + (12KCI + Aq). [397] 

Hence the origin of the name cyanogen (kvuvos yewdw). 

With a ferrous salt the precipitate is white or nearly so, but 
becomes blue in contact with the air. 

(Fe-Cl 2 + KfCfy + Aq) = K 2 ,Fe=Cfy + {2KCI + Aq). 

[398] 
12K 2 ,FeWfy + 30=0 = 2\_Fe 2 ^Cfy, + SK^Cfy + 2Fe 2 3 . 

Blue. 

With cupric salts we have a red precipitate. 

(2Cu-0 2 =S0 2 + K^Cfy + Aq) = 

Cu^Cfy -f (2K 2 =0 2 =S0 2 + Aq). [399] 

The soluble ferrocyanides, as a rule, crystallize readily, and 
the crystals usually contain several molecules of water, thus: — 

(NH^.Cfy. 3H„0, (NH<),K=Cfy, (NH,\,K 2 =Cfy, 

Na.Cfy . 12H.O, NaJQCfy . 6H 2 0, Ba^Cfy . 6H 2 0, 

K 2 ,Ba=Cfy. 3Z/ s O, Zn=Cfy . SH 2 0, (C 2 H & \iCfy.6H 2 0. 

423. Ferricyanides. — By passing CI -CI through a solution 
of KfOfy a compound is formed, IQ[Cfy.^ containing the 
hexad radical (Cfy-Cfy)% which sustains the same relation to 



[§424. CARBON AXD NITROGEN. 471 

Cfy that T£ bears to [7Y 2 ]I. On evaporating the solution we 
obtain the salt in deep-red crystals, which are an article of 
commerce under the name of red prussiate of potash. 

(.KKQfcl + 2 ^'« + M)- [400] 

Other ferricyanides may be obtained from the potassium salts 
by metathesis. 

H^Qfy % l NagCfy % -\.H % 0, NaJi^Cfy^ K^Ba^C/y^. 3H. 2 0. 

"With a solution of potassic ferricyanide ferrous salts give a 
deep-blue precipitate called Turnbull's blue. 

(iFe-Ok + mCfy,l + Aq) = 

jycow + ( &KCl + A i)- [4oi] 

Ferric salts, on the other hand, give no precipitate, and it 
will be noticed that, while these salts give a blue precipitate 
with the ferrocyanides, the ferrous salts give a blue precipitate 
only with the ferricyanides. Hence, a simple means of distin- 
guishing the two classes of salt. 

424. Other Compounds of Cyanogen. — Chlorine forms with 
cyanogen three polymeric compounds. 

Cy-Cl (Sp. Gr. 30.7), (Cy^-Ch (Sp. Gr. 61.5), 

Gas. Liquid. 

(Cy,yCk (Sp. Gr. 92.1). 

Solid. 

In like manner there are three polymeric oxygen acids. 
H-O-Cy, Hf0.f(Cy 2 ), &8 s Of(Cfo). 

Cyanic Acid. Dicyanic Acid. Cyanuric Acid. 

The tendency to polymerism (70), here manifested, is a re- 
markable feature of the cyanogen compounds, and gives rise to 
products of great complexity, most of which, however, have been 
but little studied. Their condensed molecules are evidently 
held together by complex radicals formed by the coalescing of 
several atoms of cyanogen, and it is evident that the atomicity 
of such radicals must be equal to the number of elementary atoms 
of any one kind, nitrogen or carbon, of which they consist. On 
the same principle the constitution of the ferro- and ferri-cyan- 
ides, as well as that of paracyanogen, may be explained. 



472 CARBON AND NITROGEN. [§425. 

425. Cyanates. — Cyanic acid, referred to above, forms an 
important class of salts which have a great theoretical interest 
on account of the remarkable transformations of which many of 
them are susceptible. Potassic cyanate is readily prepared by 
dropping litharge into the fused cyanide, or ferrocyauide, so 
long as the oxide is reduced. 

KC y + PbO = K-0~Cy + Pb. [402] 

In order to crystallize the salt the fused mass should be ex- 
hausted with alcohol of 80%, since on evaporating an aqueous 
solution the salt is slowly decomposed. The same change takes 
place rapidly when the salt is heated with potassic hydrate. 

K-0-CN+ K-0-H+ H 2 0=z K/OfCO -f NH Z . [403] 

When potassic cyanate is mixed in solution with ammonic 
sulphate a metathesis takes place, but the resulting ammonic 
cyanate is at once transformed into a remarkable compound- 
ammonia or amine (167) called urea, 

NH+ 0- CN= H 2 ,mNf CO, [404] 

and by this reaction the synthesis of this complex organic pro- 
duct was first obtained. 

The most interesting of the cyanates are the compounds called 
cyanic ethers, in which methyl, ethyl, &c. are the basic radicals. 
They are easily obtained, 

K- 0- Cy + K. 0,H b = 0,=S0 2 = Kf 2 =S0 2 + C 2 H f 0- Oy, [405] 

Distilled together. 

and the investigation of the many wonderful transformations of 
which they are susceptible was one of the most important steps 
in the progress of organic chemistry. 

As cyanic acid when heated with an excess of potash yields 
ammonia, so these cyanic ethers yield various amines. 

H-0-ON+ 2K-0-H= K 2 =0rC0 + H,H,H=-K 

[406] 
C 2 H f O-CN + 2K- 0-H=z K 2 = Of CO + H.F. C 2 FT^K 

Ethylainine- 

The following reactions are equally instructive : — 
C 2 H f 0- CN + 2K-0-C 2 H- = K 2 = Of CO+(C, H^N. [407] 

Triethylaniine. 



§427.] CARBON AND HYDROGEN. 473 



G i H 5 -0-CN+ H-O-C^O = 

ff,C 2 H 5 ,CJI*0^ + C0 2 . [408] 



Acetic Acid. 

Ethylacetiunide. 



2C 2 HfO-CJV+ H 2 = Jr 2 (C,H^N.,= CO + CO* [409] 

Diethylcarbauiide or urea. 

The above reactions will appear more simple if the symbols 
of the cyanic ethers are written after the ammonia type thus, 
C 2 If 5 ,CO=N, and that this is their true constitution is rendered 
probable by the fact that a body has recently been discovered 
called cyanetholine, which appears to be a true cyanic ether. 
It is made by the reaction 

Na-0-G 2 H 5 + CyCl = MCl + C 2 H f OCy; [410] 

and when acted upon by potash it yields, not ethylamine, but 
common alcohol. (Prob. 3, page 77.) 

426. Sulpho-cyanates. — By fusing potasslc cyanide with 
sulphur we obtain the sulphur salt corresponding to potassic 
cyanate, or K-S~Cy, and from this, as from the cyanate, a large 
number of compounds may be derived. Potassic sulpho-cyan- 
ate, although without action on the ferrous compounds, strikes 
a deep-red color in a solution which contains the least trace of 
a ferric salt, and for this reason is a very useful reagent. 



CARBON AND HYDROGEN. 

427. "Organic Chemistry." — It has already been stated that 
organized beings consist of materials composed chiefly of carbon, 
hydrogen, oxygen, and nitrogen ; but few as are the chemical 
elements concerned in the processes of organic life, nevertheless 
the number of compounds which have been discovered in the 
tissues of animals and plants, or formed by their chemical met- 
amorphosis, is exceedingly great. Such compounds are called 
Organic Compounds, and in works on chemistry they are usually 
studied together under the separate head of Organic Chemistry. 

While the molecules of mineral compounds consist for the 
most part of only a few atoms, those of organic compounds fre- 
quently contain a very large number, and the diversity in or- 
ganic chemistry is obtained, not by muhiplying the number of 
elements, but by varying the molecular grouping. It was for- 



474 CARBON AND HYDROGEN. [§428. 

merly supposed that the great complexity thus produced was 
sustained by what was called the vital principle ; but although 
the cause which determines the growth of organized beings is 
still a perfect mystery, we now know that the materials of which 
they consist are subject to the same laws as mineral matter, and 
the complexity may be traced to a peculiar quality of carbon 
already described. 1 The atoms of carbon are prone to combine 
among themselves, and the same tendency which appears in 
several of the elements to a limited extent is developed in the 
case of carbon to a very high degree. Carbon is the skeleton 
of an organic compound in a peculiar sense. Its atoms, locked 
together like so many vertebras, form the framework to which 
the other elements are fastened, and thus a complex molecular 
structure is rendered in a wonderful measure compact and stable. 

Organic chemistry is simply the chemistry of the compounds 
of carbon, and has no distinctive character except that which 
the peculiar qualities of this singular element give. More- 
over, although in a compendium of the science it may be con- 
venient, or even necessary, to distinguish between mineral and 
org tnic chemistry on account of the great preponderance and 
importance of the compounds of carbon ; yet in a work on Chem- 
ical Philosophy, where the object is not to enumerate facts, 
there seems to be no good reason for departing, in the ca^e of 
this single element, from the general scheme, or treating it 
more fully than is required to illustrate the new and important 
principles which it presents to our notice. Indeed, in an ele- 
mentary work no other course is possible, since a mere list of 
the known compounds of carbon would fill a large volume. 

428. Hydrocarbons. — If we conceive that the carbon atoms 
of the successive molecules are held together by the smallest 
possible number of bond-, then, as shown in (34), the symbols 
of the possible hydrocarbon compounds of this cla^s would be 
expressed by the general symbol C n H 2n + 2 , and each number of 
the series would d ffer from the preceding by CH 2 . Again, if 
we conceive that the skeleton of carbon atoms, instead of pre- 
senting at either end an open affinity as in Fig. a, forms a 
closed chain as in Fig. b, the hydrocarbon atoms of this second 
class would be expressed by C n H 2n , and form another series with 
a constant difference as before of GH 2 . Lastly, if we start with 

1 The student should very carefully review (34) in this connection. 



§428.] CARBON AND HYDROGEN. 475 

a nucleus of carbon atoms grouped together as in Fig. c, form- 
Fig, a. Fig. b. Fig. c. 
, G s Q -_ Q 

-G G- 

-G-G-G-G-G-G- - ~G G- 

v G * G - G 

ing the hydrocarbon G^H^ and add to this successive incre- 
ments of GH 2 , we obtain still a third series of hydrocarbons 
expressed by the symbol G n H 2n _^ 

Each of the above symbols represents a series of actual com- 
pounds, of which many members are known, as shown in the 
table on page 477. Moreover, the hydrocarbons of any one 
series all sustain the same general relations to chemical reagents, 
undergo similar changes when exposed to the same influences, 
and present a regular gradation in their physical properties cor- 
responding to the change in their composition. Compounds so 
related are said to be homologues, and such a series is called an 
homologous series. 

Obviously, however, the three series, whose relations have 
been just described, do not include all the possible hydrocarbons, 
for, starting with any one of the more complex molecules of the 
first class, in which the carbon atoms are united by the smallest 
possible number of bonds, we may assume that the open bonds 
are successively closed two by two by the more intimate union of 
the carbon atoms among themselves, and we shall thus obtain a 
derived series, whose successive members differ by the quantity 
H 2 . The general symbol of such a series would be G n H {n _ m)Jr2 , 
the first term being G n H 2n + 2> m standing for the number of 
the required term counting from the first. Compounds thus 
related are termed isologues, and it is obvious that tho^e hydro- 
carbons in the three series of homologues exhibited above, 
which contain the same number of carbon atoms, are members 
of the same series of isologues ; but it is also obvious that be- 
sides these three an indefinite number of parallel homologous 
series are theoretically possible. The student will best under- 
stand the relations of this scheme by tabulating the possible 
compounds, arranging the homologues in parallel columns with 
the isolosrues on the same horizontal line. He will thus see 



476 CARBON AND HYDROGEN. [§428. 

that there is no limit to the number of hydrocarbons, except 
that fixed by the instability of the resulting molecules. 

A table, prepared as just directed, would not, however, ex- 
hibit all the possibilities in this scheme of the In drocarbons, 
since we may conceive of the atoms of each of the more com- 
plex compounds as arranged in different ways, and thus giving 
rise to one or more isomeric modifications. For example, we 
may construct the symbol of the hydrocarbon C A H i{) as indicated 
by either of the rational formulas (C~ Q- C-C)*H 10 or C=( CJI S ) 3 ,II, 
and with a little ingenuity the student will readily discover in 
any case the number of such commutations possible, only he 
must carefully distinguish between a more arbitrary change in 
the relative po-ition of the atoms and a fundamental difference 
of arrangement. The last alone implies a difference of quali- 
ties in the substance which the formulas represent, and indicates 
the possibility of isomeric modifications. Review in this con- 
nection (70). 

It must not be supposed that all the hydrocarbons which our 
theory prefigures are actually possible, that is, represent com- 
pounds which either have been or may be isolated ; for as yet 
the theory has taken into account but one condition, namely, the 
atom-fixing power of carbon, and many causes may intervene 
to render unstable the compounds which are, from this one point 
of view, theoretically possible. As the number of carbon atoms 
increases, a condition is soon reached, when, if we may so ex- 
press it, the molecule cannot sustain its own weight, and in all 
cases the atoms must be so grouped as to preserve certain polar 
relations between its several parts. As yet, however, we do 
not understand the laws which determine molecular stability, 
and cannot, therefore, foresee the result in a given case, so that 
we are unable to control our algebraic method. Still, with all 
this uncertainty the theory has its value, and not only serves 
for the time to classify our facts, but gives us one of those 
glimpses of the order of creation which are the greatest privi- 
lege that the student of nature enjoys. 

But with all the limitations which the conditions of stability 
impose, the number of possible hydrocarbons must be very large, 
and the compounds actually known can form but a very small 
portion of those which may hereafter be isolated. The series of 
homologues given on page 477 include the greater part as well 



§428.] 



CARBON AND HYDROGEN. 



477 



as the mo«t important of the known compounds of this class. 
Of other series a few members here and there have been recog- 
nized, but in regard to mo t of these our knowledge is imperfect 
and uncertain. Many hydrocarbons are found in a free state 
in nature, but mixed together in the petroleums, and in those 
combustible gases like tne fire-damps of coal- nines which are 
evolved from the earth in many localities. Others are found 
among the prod icts of the dry distillation of coal, wood, or other 
organic tissues, and in either case the individual compounds are 
isolated by various processes of fractional distillation. Others, 
again, have been obtainel by various chemical reactions, and 
of these a few of the more characteristic are given below : — 



Marsh Gas Series 






Acetylene Series. 




C TT 

^n L1 2n + 2. 


B. P. 




C n ™2n-2 




Methylic Hydride 


CH, 




Acetylene 


C 2 H 2 


Ethylic Hydride 


C. 2 H 6 




Allylene 




C 3 Hi 


Propylic Hydride 


C Z H S 




Crotonyl 


ene 


C!jif 6 


Butylic Hydride 


£4^10 


0°.02 


Valerylene 


C 5 H 8 


Amylic Hydride 


C r> Ha 


3(P.2 


Allyl? 




CqH 10 


Hexylic Hydride 


Q-^u 


61°.3 








Heptylic Hydride 


C 7 H l6 


90°.4 








Octylic Hydride 


Q-^18 


119°.5 








Nonylic Hydride 


C§H 2Q 


150°.8 








Olejiant 


Gas Series 






Essential Oils. 




CA 


B. P. 




C n H 2n-4 




Ethylene 
Propylene 


CM, 


— 17°.8 


Oil of Turpentine 


C 10 H 16 


Butylene 


C 4 H 8 


+33°.0 








Amylene 


Cr.ffto 


55°.0 








Hexylene 


C(iH xi 


39'.0 








Heptylene 


C 7 IT U 


55°.0 








Octylene 
Nonylene 




95°.0 
123 J 




Phenyl Series. 




Decatylene 


^10-^20 


174°.9 




C H 


B. P. 


Endecatylene 


C n H n 


193'.8 




n 2n — 6 




Dodecatylene 


C l2 H 2i 


213°.2 


Benzol 


CrH, 


82° 


Tridecatylene 


^13"26 


235° 


Toluol 


C 7 H 8 


111° 


Cetene 


C r ,ff 32 




Xylol 


C«-*M0 


129° 


Cerotene (parafflne) 


^27-^-4 


270° 


Cumol 


Q#12 


148° 


Melene 


^30-^60 


375° 


Cymol 


^10-^14 


175° 



Several of the terms in the above series are represented by 
at least two isomeric compounds. Thus we find in the Penn- 
sylvania petroleums, mixed with the last six members of the 
marsh gas series, five other hydrocarbons, C±H l0 to C 8 ff 18 , iden- 



478 CARBON AND HYDROGEN. [§429. 

tical in composition, but having boiling-points uniformly eight 
degrees higher. The common difference between these boiling- 
points (which have been determined with great accuracy) is 
vevy nearly 30°, and it is probable that a similar constancy 
would appear in all series of truly homologous compounds, and 
the discrepancies noticeable in several members of the series as 
above exhibited are probably to be referred to the fact that 
bodies are here included which do not belong to the same type. 
429. Marsh Gas Series. C n H, n+2 , — Molecules having this 
composition must necessarily be closed and saturated. Hence 
the hydrocarbons of this class are indifferent bodies, but they 
readily yield substitution compounds containing chlorine and 
bromine. Thus, when we act on marsh gas (CJI^) with chlo- 
rine, hydrochloric acid is formed, and we obtain either CH 3 Cl, 
CHClfr CCl 4 , or C, the products of the reaction varying with 
the conditions of the experiment and the proportions of the fac- 
tors. Marsh gas may be obtained perfectly pure from zinc 
methide (324), which is decomposed by water, as shown by the 
following reaction : — 

Zn-{CH,) 2 + 2H 2 = Zn = 2 -H 2 -f 2CH* [411] 

By a similar reaction ethylic and amylic hydrides can be ob- 
tained from zinc ethide and zinc amylide. 

The first member of the series has long been known as a 
product of the decomposition of vegetable tissue under water, 
and hence the trivial name Marsh Gas. It is the chief constit- 
uent of the fire-damp of coal-mines, and of common illuminating 
gas obtained by the dry distillation of coal. It is most conven- 
iently prepared by heating potassic acetate with a large excess 
of potassic hydrate mixed with quicklime. 

K-0-C 2 H z O + K- 0-11= KfOfCO + OSS* [412] 

It can also be obtained by either of the following reactions, but 
they have only a theoretical interest. 

CCl, + ±ff-H= ARCl + CH* [413] 

CHCl z + 2>H-H= SRCl + CH±. [414] 

®^ 2 + 2IU 2 ^ + 4Cn = 4ClI$ + « 4 . [415] 



§430.] CARBON AND HYDROGEN. 479 

The first two reactions are obtained by reducing carbonic chlo- 
ride or chloroform with nascent hydrogen, the la>t by passing 
H 2 S gas mixed with GS 2 vapor over ignited copper. 

Marsh gas has no sensible qualities, and has never been lique- 
fied. Like the other members of the series it is highly combus- 
tible, and burns with a luminous flame. 

Marsh gas and its homologues may be regarded as hydrides 
of radicals having the general form C n II 2n+1 , and we are al- 
ready acquainted with many compounds in which these atomic 
groups manifest a marked individuality. Ethylic iodide is easily 
prepared, and by acting on this compound with zinc we obtain 
a hydrocarbon which may be regarded as the corresponding 
radical substance. 

2 C 2 H 5 -I+ Zn — Znl 2 + CJBfCJR* [416] 

In like manner similar products may be obtained with several 
of the homologous compounds, and by using iodides of two radi- 
cals simultaneously the so-called double or mixed radicals may 
be produced. 

CHs-I+ C 2 ff 5 -I+ Zn = Znl 2 -f Cff 3 -C 2 B 5 . [417] 

These hydrocarbons, however, are all isomeric, if not identical, 
with the normal terms of the marsh gas series. 

430. Olefiant Gas Series. C n H 2n% — Molecules of this type 
are not necessarily closed, but are capable of fixing two addi- 
tional monad atoms, and of acting as dyad radicals. The first 
member of the series was discovered by an association of Dutch 
chemists in 1795, who, noticing its characteristic property of 
combining directly with chlorine, called it Olefiant (oil making) 
Gas, because the product of this union is a thick flowing liquid. 
This product, long known as the Oil of the Dutch chemists, is 
ethylene chloride, C 2 H±Cl 2 . Ethylene bromide and ethylene 
iodide may be formed in a similar way, and the tendency to 
form compounds of this type distinguishes this class of hydro- 
carbons, which are called, for this reason, ole fines. Moreover, 
the hydrogen atoms of the bivalent radical may all be replaced 
by chlorine or bromine, and the resulting compound still retain 
the same typical character. This is shown by the following 
reactions : — 

2 ff, + Br-Br = ( C 2 H,)-Br 2i [418] 



430 CARBON AND HYDROGEN. [§431. 

(C 2 IJ 4 )-Br 2 + K-0-H= C 2 fI 3 Br + KBr -f H 2 0, [419] 

G 2 H 3 Br -f- Br-Br = ( C 2 R 3 Br)=Br 2 , [420] 

(G 2 II 3 Bry-Br. 2 + K-O-H— C 2 H 2 Br 2 + KBr + #,(9, [421] 

which may be repeated with the successive products, until at 
last we ob ain C 2 Br 4 and (G 2 Br 4 )=Br 2 as the final results. 

Oldfiant gas is m>st readily obtained by heating a'cohol with 
several lim j s its volume of strong sulphuric acid. The reaction 
is somewhat complicated, but the result is a dehydration of the 
alcohol, and the same effect may be produced with zincic 
chloride (323). 

C, FT, — H 2 0= C 2 ff,. [422] 

Like marsh gas this aeriform hydrocarbon has no sensible 
qualities save a slight odor, due probably to a trace of ether. 
It has, however, been liquefied, and is slightly soluble in water. 
Containing twice as much carbon in the same volume, it burns 
with a more luminous flame than the lighter gas, and the illumi- 
nating power of coal-gas is due in no inconsiderable measure to 
its presence. Olefiant gas combines directly, not only with 
chlorine, bromine, &c, but also with the hydrogen acids. 

2 H, -f HI= C 2 HJ. [423] 

Moreover, it unites with hypochlorous acid, forming a chlor- 
hydrine. 

C 2 H, + H-0-Cl=( C 2 H,yiIo, CI. [424] 

These reactions of olefiant gas illustrate in general the chemi- 
cal relations of this series of hydrocarbons ; but it is probable 
that several of those included in the list on page 477, although 
isomeric with terms of the series, are really formed after a dif- 
ferent type. A large number of them are only known as con- 
stituents of petroleum or products of dry distillation, and have 
not been prepared by any intelligible process. 

431. Acetylene Series. C n H 2ll _ 2% Acetylene. — This gas is 
formed by the direct union of its elements, when the current 
from a powerful voltaic battery passes between carbon poles in 
an atmosphere of hydrogen. It may also be obtained by the 
action of water on potassic carbide. 

K 2 C 2 + 2ff 2 = 2K-0-IT+ C 2 H 2 . [425] 



§433.] CARBON AND HYDROGEN. 481 

It is not unfrequently a product of the incomplete combustion 
of bodies containing carbon and hydrogen, and it may also be 
prepared in other ways. Acetylene acts as a dyad or tetrad 
radical, combining with nascent hydrogen to form C 2 H 4 (ethy- 
lene), with bromine to form G>H 2 Br 2 or C 2 JT 2 Br 4 , and with hy- 
drobromic acid to form G 2 H z Br or C 2 H±Br 2 . It is not yet de- 
termined whether these bodies are identical with the isomeric 
compounds of the olefiant gas series. When the gas is passed 
through a solution of cuprous chloride in ammonia, a highly 
explosive compound is formed as a red precipitate, which has 
the composition (C 2 H[_Ca 2 ~]) 2 =0, and acts as a basic anhydride. 
The other hydrocarbons of the series have similar chemical re- 
lations, but have not been thoroughly studied. 

432. Allyl. — When allylic iodide is digested with sodium 
and distilled, we obtain a hydrocarbon which has the composi- 
tion CqH^ 

Na-Na + 2{C 3 H 5 )-I= 2Na-I + C 3 IIfC 3 ff 5 . [426] 

This product, moreover, unites directly with one or two mole- 
cules either of Br-Br or H~I, and in general its chemical rela- 
tions are those of a homologue of acetylene. But, as the above 
reaction indicates, it may also be regarded as the radical sub- 
stance (22) corresponding to allyl, and this view is sustained 
by the fact that there is an isomeric hydrocarbon having similar 
chemical relations, but different physical qualities, which is 
more probably the fifth member of the acetylene series. 

433. Essential Oils. C n H 2 n-i. — Oil of Turpentine and many 
other essential oils have a composition represented by the sym- 
bol CtfHiQ, and there are a few others which, although also iso- 
meric, must be represented by a multiple of this symbol ; but 
no other members of the series are known. Oil of turpentine 
combines both with the hydrogen acids and with water, forming 
compounds in which ((7 10 ZT 16 ) acts either as a dyad or a tetrad 
radical, and others in which the double molecule acts as a hexad. 
radical. Thus we have 

{^wB x ^H,Cl, (C l0 H lfi )=H 2 ,Cl 2 , (C^H^yH^Cl, {C w H^)lH v Cl z . 

Exposed to the air oil of turpentine absorbs oxygen, yielding a 
resinous product, and the same is true to a greater or less de- 
gree of the other essential oils. They all appear to have simi- 
21 EE 



482 CARBON AND HYDROGEN. [§434. 

lar chemical relations, and are singularly susceptible of allo- 
tropic conditions ; but on what the differences between these 
isomeric bodies depend we are as jet ignorant. 

434. Phenyl Series. O n H. ln _^ — The hydrocarbons of this 
class are found in coal-tar and Rangoon petroleum, and are iso- 
lated by fractional distillation. Benzol, or benzine, is very 
much used in the arts, but the commercial product is more or 
less mixed with the associated hydrocarbons. When pure, 
benzol becomes solid at a low temperature, melting only at 5°,5. 
Benzol may be obtained artificially by heating benzoic or 
phthalic acid with an excess of lime. 

0:11,0, + 0(10= OaO0 3 -f 6 ff 6 . 

Benzoic Acid. Benzol. 

[427] 
C„ff e O t + 2 C'a = 2 Ca CO, -f C H & . 

Phthalic Acid. Benzol. 

Benzol, when treated with chlorine or bromine, yields a num- 
ber of substitution products. By the action of nitric acid we 
obtain (31) 

Nitro-benzol 6 ff d (WO,), 

Dinitro-benzol C^H^NO^^, 

and when acted on by reducing agents (as zinc and hydrochloric 
acid, sulphuretted hydrogen, &c), nitro-benzol is converted into 
aniline (1^7), and thus becomes the source of the aniline dyes. 

6 ff 5 (JV0 2 ) + 3If 2 S=: C&{NH 2 ) + 2H 2 0+ S 3 . [428] 

The other hydrocarbons of this series may be regarded as 
containing the same group of carbon atoms as benzol, and as 
derived from it by replacing one or more of its hydrogen atoms 
with the radicals methyl, ethyl, or amyl. It is evident that by 
replacing several atoms of hydrogen with methyl we should ob- 
tain a body of the same composition as by replacing a single 
atom with a radical richer in carbon, and we have abundant 
evidence that compounds thus obtained, though isomeric, are 
not identical. 

The radical 6 lf 5 , called Phenyl, appears to be the nucleus of 
all the hydrocarbons of this series. By acting on boiling benzol 
with bromine, we obtain the bromide of this radical, 

C Q H, + Br-Br = 0,H f Br + H-Br, [429] 



$435.] CARBON AND HYDROGEN. 483 

and when this product is treated with sodium a hydrocarbon is 
formed which is regarded as the corresponding radical substance. 

2 C 6 H 5 -Br + Na-Na = C 6 H 5 - C & H b + 2NaBr. [430] 

Benzol is then phenylic hydride, and its homologues are hy- 
drides of more complex radicals, which may be designated as 
methyl-phenyl, dimethyl-phenyl, &c. Besides the hydrocarbons 
included in the five series just described we know also a few 
others. Of these the best studied are phenylene, C^H^ and 
cinnamene, C%H^ corresponding to the symbol C n H~ 2n _ 8 , and 
napthaline, C W II S , corresponding to C u H 2n _- [2 . They all com- 
bine with chlorine and bromine, and have in general the chem- 
ical relations of artiad radicals. The last of these especially 
yields with the>e elements, besides the direct compounds, a very 
large number of substitution products, and the careful investiga- 
tion of these bodies by Laurent was an important step in the 
progress of chemistry (31). 

435. Hydrocarbon Radicals. — It is evident from the prin- 
ciples developed in (22) and (28), and still further illustrated 
in (34), that, by eliminating successive atoms of hydrogen, 
each of the possible hydrocarbons of the scheme exhibited 
above may yield a series of compound radicals, and that the 
atomicity of such radicals is equal in any case to the number 
of hydrogen atoms thus lost. 

Such of these radicals as contain an even number of hydro- 
gen atoms are necessarily artiads, and isomeric with either ac- 
tual or possible hydrocarbons. Moreover, it follows from (428) 
that we may have several artiad radicals isomeric w r ith each of 
the more complex compounds. Thus we may have two radicals 
(G 2 ff 2 ) = and (C 2 IT 2 )= isomeric with acetylene, and the same is 
true of each of the homologues of this hydrocarbon. Indeed, 
parallel to each series of hydrocarbons, except the first, we may 
have one or more series of artiad radicals isomeric, term by 
term, with the normal compounds, and the number of po-sible 
isomers in any case is the same as the number of the series in 
the order of isologues (428). It is, however, an open question 
whether such hydrocarbons as ethylene or acetylene are essen- 
tially different from the radicals of the same composition (69), 
and we do not distinguish the radicals by separate names. 

The hydrocarbon radicals which contain an odd number of 
hydrogen atoms are necessarily perissads, and cannot, without 



484 CARBON AND HYDROGEN. [§43G. 

reduplication, exist in a free state [416], [417], and [426], 
Nevertheless, the radicals homologous with methyl and phenyl 
play such an important part in numberless chemical reactions, 
and preserve their integrity through so many changes, that, al- 
though only known in combination, their individuality is as well 
marked as that of the elements themselves. Hence it is with 
reason that they have received distinctive names. With most 
of these the student is already familiar, but to those previously 
noticed we may here add Vinyl, C 2 H 3 -, Glyceryl, C 3 H-= (the 
trivalent condition of allyl), and the radical of chloroform, CH=, 
which are all important perissads. 

436 Oxygenated Radicals. — - Unless associated with some 
very powerful basic radical, like the alkaline metals, the simple 
hydrocarbons always form basic or positive radicals (40). To 
every such radical, however, corresponds an acid or negative 
radical having the same atomicity, which is generated by re- 
placing a portion of the hydrogen with oxygen (34). Thus : — 



Methyl 


OH 3 


yields Formyl 


CHO 


or CO-H, 


Ethyl 


o 2 h 5 


" Acetyl 


c 2 h 3 o 


« co-ch 3 , 


Propyl 


CA 


" Propionyl 


3 H 6 


" CO- CM* 


Butyl 


CA 


" Butyryl 


C 4 H 7 


« CO~C 3 H 7 , 


Amyl 


GAn 


" Valeryl 


GAO 


" GO-CA 



Allyl C 3 H 5 « Acryl C 3 H 3 " CO-C 2 H 3 , 

Ethylene CA yields Glycolyl CO-C # 2 and Carbonyl (C0) 2 
Propylene C 3 FT 6 " Laetyl COCA " Malonyl (CO)=Cff s1 
Acetylene C 4 # a " Acetonyl CO-CA " Succinyl (CO)=C z H\. 

If the theory of (416) is correct, it is evident that the virtue 
of these oxygenated radicals depends entirely on the number of 
atoms of carbonyl which are generated in the hydrocarbon 
radical, and we find that only those atoms of hydrogen can be 
replaced which are so related to the molecule that the atoms of 
carbonyl thus formed may have an open bond, and by the 
addition of Ho be converted into oxatyl. Hence the number 
of oxygen atoms which can thus be introduced into the radical 
can never exceed its atomicity, 'Und the basicity of the acids, 
formed by the union of the resulting negative radicals with Ho, 
is equal to the number of oxygen atoms which any such nega- 
tive radical contains. 



§438.] MONATOMIC COMPOUNDS. — MARSH GAS SERIES. 485 



ALCOHOLS AND THEIR DERIVATIVES. 

437. Definition. — The name of alcohol is applied to a class 
of bodies which resemble common vinic alcohol chiefly in that 
under like conditions they are susceptible of similar reactions. 
They are produced in a variety of processes, especially by fer- 
mentation ; but the reactions cannot usually be traced. They 
may be regarded as hydrates of the hydrocarbon radicals (40), 
or as formed from the hydrocarbons themselves by replacing 
one or more atoms of hydrogen with hydroxyl, and their atom- 
icity (43) depends on the number of atoms of Ho thus intro- 
duced into the molecule. Hence we have monatoinic, diatomic, 
triatomic alcohols, &c, and these are still further subdivided 
according to the class of hydrocarbons from which they are de- 
rived. Moreover, each alcohol is one of a group of compounds 
which may be derived from each other by simple reactions, not 
affecting the arrangement of the atoms in the carbon skeleton 
that may be regarded as the nucleus of the group. The com- 
pounds thus related have frequently little in common, and in 
more extended works would be classed under their appropriate 
heads. Our only object is to exhibit a few of the general prin- 
ciples and wonderful relations which the study of organic chem- 
istry has revealed, and this will best be gained by associating 
with each class of alcohols those of their derivatives which have 
the same atomicity. 

MONATOMIC COMPOUNDS. 
1. Marsh Gas Series. 

438. Alcohols. — This very important class of compounds 
may be regarded as derived from the normal hydrocarbons of 
the marsh gas series by replacing a single atom of hydrogen 
with Ho, and consequently they are hydrates of the radicals of 
the methyl series (40). Of these bodies the following are 
known : — 

Boiling-point. 

Methylic Alcohol CHfO-H 66°.5 

Ethylic Alcohol C 2 H f O-H 78°.4 

Propylic Alcohol C s H 7 -0~H 9G° 

Butylic Alcohol 4 H Q -OH 109° 



486 ALCOHOLS AND THEIR* DERIVATIVES. [§438. 







Melting-point. 


Boiling-point 


Amylic Alcohol 


C,H n -0-H 


— 20° 


132° 


Hexylic Alcohol 


CJBkO-h 






Heptylic Alcohol 


C 7 H lf O-H 






Oetylic Alcohol 


C H H lf O-H 




178° 


Cetylic Alcohol 


CiqH&O-H 


50° 




Cerotic Alcohol 


CvHn-O-H 


79° 




Melissic Alcohol 


C w H a -0-H 


' 85° 





The lower members of the series are liquids, the higher solids, 
and the boiling-point increases about 19° for every addition of 
CH 2 . The following reactions illustrate the production of 
methylic alcohol from marsh gas : — 

Off, + CI- CI = H CI + CH 3 - CI, [431] 

CH Z - CI + Aff-0- G 2 ff s 0=zAgCl+ CH,- 0- 0& 0, [432] 

CH z -0-C 2 H z O + K-0-H=z K-0-C 2 H,0 + CH 3 -0-H; [433] 

and the same method applied to the homologues of marsh gas 
yields other members of the alcohol series. 

We may also start with olefiant gas, and having combined 
this with HCl we may convert the C 2 H- a Cl thus formed into 
common alcohol by the same series of reactions as before, or we 
may reach the same result by combining olefiant gas with sul- 
phuric acid and distilling the product with water. 

Rl OfS0 2 + C 2 R 4 = H, C 2 ff 5 = 2 =S0 2 . [434] 

H,C 2 HfOiS0 2 + H~0-H= RfO.fSO, + C 2 H f 0-H. [435] 

Propylic alcohol may be obtained from C 3 H 6 by similar re- 
actions, but these processes applied to the other members of the 
olefiant series either give no results or yield compounds which, 
although resembling the true alcohols, and isomeric with them, 
manifest in their reactions an essential difference of molecular 
structure. These bodies have been called pseudo-alcohols. 

By means of the following reactions we may ascend from one 
member of the alcohol series to the next higher : — 

C 2 JI 5 -0-R+ JI 2 =0 2 =S0 2 = &,C 2 H 5 =O 2 =S0 2 + H 2 0. [436] 



§439.] MONATOMIC COMPOUNDS. — MARSH GAS SERIES. 487 

K, ti 2 Hf OfSp % + K- OJV = K 2 = 2 =S0 2 -f C 2 H f CK [437] 

C 2 H 5 - CJST+ 2H-H= H,H y C z HfN. [438] 

2(H,H,C,HfN)-\-N 2 0,= 

2C & H f O-H-{- H,0-\- 2N-N. [439] 

Common alcohol is always obtained in the arts by the fer- 
mentation of grape sugar (480), and other compounds of the 
series are not uufrequently formed in small amounts during the 
same process. 

The typical hydrogen of the alcohols may be replaced by 
sodium or potassium. 

2H-0- C 2 H 5 -f K-K = 2K- 0- C 2 ff 5 + H-H. [440] 

An alcohol in which the oxygen has been replaced by sul- 
phur may be obtained by the following reaction : — 

K, C. 2 Hf 2 =S0 2 + K-S-H= K 2 = 2 =S0 2 -f C 2 H 6 S-H. [441 ] 

This sulphur alcohol is called mercaptan, and a corresponding 
selenium alcohol is also known. 

By the action of oxidizing agents the alcohols are converted 
first into aldehydes and then into acids, 



C 2 H,-Ho + = C 2 ff,0-fT-\- H 2 0, 

Alcohol. Aldehyde. 

C^O-H+O — OJR*0-R6s 

Aldehyde. Acetic Acid. 



[442] 



but only in a few cases can the process be arrested at the first 
stage. 

439. Fat Acids. — The acids formed by the oxidation of the 
monatomic alcohols belong to a remarkable series of organic 
compounds, of which more members are now known than of 
any other. These acids may be regarded as hydrates of the 
oxygenated radicals of the methyl series (40), (436), or as 
formed from the hydrocarbons homologous with marsh gas by 
replacing one atom of hydrogen with oxatyl (416). The fol- 
lowing are known : — 



488 ALCOHOLS AND THEIR DERIVATIVES. [§439. 











Melting- 
poiut. 


Boiling 
point. 


Formic Acid 


H-O-CHO 


or 


Ho-(CO-H) 1 


+i° 


100° 


Acetic Acid 


H-0-C 2 H 3 


a 


Ho-(CO-CH 3 ) 


+17< 


117° 


Propionic Acid 


H-0-C 3 H b O 


it, 


Ho-(CO-C 2 H b ) 




141° 


Butyric Acid 


H-O-CJI^O 


u 


Ho-{CO-C 3 H 7 ) 


—20° 


161° 


Valeric Acid 


H-0-C r H 9 


a 


Ho-(CO-CJl 9 ) 




175° 


Caproic Acid 


H-0-C Q H n O 


a 


Ho-(CO-C b H n ) 


+5° 


198° 


(Enantlrylic Acid 


I H-0-t\H l3 


« 


Ho-(CO-C 6 H u ) 




212° 


Caprylic Acid 


H-0-C s H Vj O 


u 


Ho-iCO-C^) 


14° 


236° 


Pelargonic Acid 


H-0-C 9 H„0 


tt 


Ho-(CO-C 6 FT 17 ) 


18° 


260° 


Capric Acid 


H-O-C 10 H 19 O 


u 


Ho-(CO-C 9 H 19 ) 


27° 




Laurie Acid 


H-0-C l2 H n3 


u 


Ho-(CO-C n H i3 ) 


44° 




Myristic Acid 


H-0-C u H 27 


u 


Ho-iCO-CJl^) 


54° 




Palmitic Acid 


H-0-C 16 H 31 


u 


Ho-(CO-CJl 31 ) 


62° 




Margaric Acid 


H-O-C^H^O 


u 


Ho-(CO-C 16 H 3i ) 


60° 




Stearic Acid 


H-0-C 18 H 3b O 


a 


Ho-(CO-C 17 H r J 


69° 




Arachidic Acid 


H-O-C 20 H 39 O 


a 


Ho-(CO-C 19 HJ 


75° 




Behenic Acid 


H-0-C 2O H«0 


a 


Ho-iCO-C^,) 


76° 




Cerotic Acid 


H-0-C 27 H h3 


u 


Ho-iCO-CJf,,) 


78° 




Melissic Acid 


H-O-C^O 


tt 


Ho-(CO-C n U u ) 


88° 





Formic acid is found in nettles, and is secreted by ants. Va- 
leric acid is found in the valerian root, pelargonic acid in the 
essential oil of the Pelargonium roseum, and cerotic acid in 
beeswax. Chinese wax is cerylic cerotate, spermaceti cetylic 
palmitate, and the natural fats are mixtures of salts of various 
acids of the group, in which glyceryl, C 3 II 5 , is the basic radical. 
Several of these acids may be procured by the oxidation of al- 
buminous compounds. Propionic and butyric acids are pro- 
duced in some kinds of fermentation, and acetic acid is made in 
the arts in large quantities from the products of the dry distil- 
lation of wood and other similar substances. 

The formation of the fat acids by the oxidation of the corre- 
sponding alcohol is illustrated by the reactions already given 
[442]. They may also be formed from the cyanides of the 
alcohol radicals, and the method is interesting as indicating 
their molecular constitution. 



1 The student will not fail to notice that all dashes used in connection with 
the hydrocarbon radicals must refer exclusively to the carbon atoms, since the 
hydrogen atoms, being united to the carbon skeleton by their only bond, can 
present no open affinity. 



§439.] MONATOMIC COMPOUNDS. —MARSH GAS SERIES. 489 

H-CN + HCl + 2H 2 = NH± CI 4- (H- CO) -Ho. 

[443] 
C 2 H 5 - G2V+ HCl + 2H 2 = JSTH,- CI + ( C 2 H- CO) -Ho. 

So also 
C 2 H f CN+ KHo + H 2 0= (C 2 H 5 -CO)-Ko -f NH 3 . [444] 

On the other hand, when the amnionic salts of these acids are 
heated with P 2 5 they are converted back into the cyanides of 
the radicals of the methyl series, 

( CH 3 - CO)-(NH 4 )o -f 2P 2 5 == CH f CN+ Iff- O-PO* [445] 

and from the cyanide thus obtained the corresponding alcohol 
may be produced by [438], and in this way [442] is reversed. 
The acid may also be converted into the alcohol by another 
remarkable series of reactions, of which the following series is 
an example : — 

(CH 3 -CO)-Ko + (H-CO)-Ko = 

Potassic Acetate. Potassic Formate. 

( CHf CO)H -f Ko 2 - CO. [446] 

Acetic Aldehyde. Potassic Carbonate. 

\CH f CO)-H+ H-H = C 2 H f O-H [447] 

The potassic salt of the acid is first distilled with potassic for- 
mate, and the aldehyde thus obtained transformed into alcohol 
by nascent hydrogen. Starting now with ethvlic alcohol, we 
can convert it into ethylic cyanide by [436] and [437], and 
then by [433] or [444] we can produce propionic acid. Thus 
we are able to pass from one fat acid to the next as from one 
alcohol to the next, and since formic acid can be made directly 
from its elements [374] the synthesis of this whole class of or- 
ganic compounds is, theoretically at least, possible. 

All these reactions seem to indicate that the fat acids, contain 
the radicals of the methyl series united to oxatyl, and this view 
is rendered more probable by the fact that sodic acetate may be 
formed by the direct combination of C0 2 with sodic methide. 

( CH S )-Na + C0 2 = ( CH 3 - CO) -Nao. [448] 

Again, it appears that, when the acids of this series are acted 
upon by nascent oxygen in the process of electrolysis, C0 2 is 
21* 



490 ALCOHOLS AND THEIR DERIVATIVES. ' [§440. 

formed, and the radical assumed to have been previously united 
to the oxatyl is thus set free. 

2{CH f CO)-Ho +0= GH Z -CH, + R 2 0+2C0 2 . [449] 

If this theory of the constitution of the fat acids is correct, it 
is obvious that if we could replace the radical hydrogen of for- 
mic acid with the radicals methyl, ethyl, &c, we should obtain 
the successive members of the series. The direct substitution 
has not been accomplished, but with acetic ether an analogous 
series of reactions has been obtained. 

2C 2 K 5 -0-(CO-CH 3 ) -f Na-Na = 

2C 2 H b -0\CO-CH 2 Na)-\-II-H. [450] 

C 2 H h -0\CO-CH 2 Nd) + Cff s I= 

C 2 H f O-(CO-C 2 H 5 ) + NaT. [451] 

C 2 H 5 -0-(CO-CH 2 Na) + C 2 TT 5 T= 

C 2 H f O-{CO-C,H 7 ) + NaT. [452] 

440. Formic Acid, on account of its peculiar constitution as 
the first member of the series, presents some special reactions 
which are highly instructive. Thus, when heated with strong 
sulphuric acid, 

(ff-CO)-Bo = ff 2 0+ CO. [453] 

So also when acted on by chlorine gas, 

{H- CO)- Ho + CI- CI = 2TTCl + C0 2 . [454] 
It even acts as a reducing agent, 

(H-CO)-Ho + HgO = Hg + H 2 + C0 2 . [455] 

441. Acetic Acid, the acidifying principle of vinegar, is the 
best known of all the lower members of this series of com- 
pounds and the student has already become familiar with it in 
many reactions. The remarkable substitution products which 
it yields with chlorine have already been described (31), and 
the manner in which it breaks up when acted on by PCl 5 has 
also been illustrated (20). By this last reaction a chloride of 
the assumed oxygenated radical (acetyl) is obtained. 



§443.] MONATOMIC COMPOUNDS. — MARSH GAS SERIES. 491 

442. Isomers of the Fat Acids. — It is obvious that with the 
higher members of the acetic acid series one or more isomeric 
modifications are possible, depending upon the different ways 
in which the atoms of the hydrocarbon radical may be grouped 
(428). Such differences of structure have been actually real- 
ized by means of reactions similar to [450 et seq.~\, using, how- 
ever, as the starting-point, the products obtained by replacing 
two or all three of the hydrogen atoms of the acid radical in 
ethylic acetate with sodium. 

C 2 HfO-(CO-CHNa. 2 ) + 2CffJ= 

2Nal+C 2 H & -0-(CO-CH-{CH.^ 2 ). [456] 

C 2 H 5 -0-(CO-CNa z ) +3CIIJ= 

3NaI+G 2 ff 5 -0-(CO-a(C& 3 ) :i ). [457] 

By acting on these ethylic salts with K~Ho, the corresponding 
potassic salts are readily obtained, from which the acids them- 
selves may be easily set free. 

Now the first of these products is isomeric, but not identical, 
with butyric acid (boiling at 152° instead of 161°), and the 
second sustains a similar relation to valeric acid. By exhibit- 
ing the symbols graphically, the difference of structure will be 
made evident, and it will appear that, although reactions like 
[451] yield the normal acids of the series, reactions similar to 
the last must necessarily give the so-called iso-acids. It can 
also be discovered how many isomers are possible in any case. 

443. Ethers. — These compounds are the anhydrous oxides 
of the alcohol radicals (40), and our common ether, {C 2 H 6 ) 2 =0, 
may be taken as the type of the class. It is prepared by the 
action of sulphuric acid on alcohol, and the process may be di- 
vided into two stages : — 

C 2 ff 5 -0-H+ K r 2 =S0 2 = &,C 2 H<r0.fS0 2 + SI,®. 

[458] 

^c 2 ff 5 -o 2 =so 2 +c 2 ff 5 -o-H—if 2 =o 2 =so 2 +(^ 2 m 5 ) 2 ^. 

The alcohol and sulphuric acid, mixed in equivalent proportions, 
are heated in a retort, when the water and ether di-til over to- 
gether, and if the loss is supplied by fresh alcohol (flowing slowly 
into the retort through a tube adapted to the tubulature) the 
same quantity of sulphuric acid will convert an unlimited quan- 
tity of alcohol into ether. 



492 ALCOHOLS AND THEIR DERIVATIVES. [§444. 

Ether may be reconverted into alcohol by reversing the 
above reaction, thus : — 

( oja^i o + 2Kf o 2 =so 2 = 2ii, a 2 H s = o 2 =so 2 + m,®. 

[459] 
H, G 2 Hf 0.fS0 2 + H-OH= H 2 = 2 =S0 2 + O^-^Sl. 

By using in the second stage of " etherification " an alcohol 
containing a different radical, mixed ethers as they are termed 
may in some cases be obtained. 

H,C 5 R n =0 2 =S0 2 + C 2 H b O-H=. 

H 2 =0 2 =S0 2 + C^C&fO. [460] 

Other bodies of this class have been formed, thus : — 

2CH 3 -0-H+ Na-Na = 2CH,-0-Na + HH. 

[461] 
CHfONa + C 2 HJ= NaI-\- GH & -0-C 2 H 5 . 

444. Compound Ethers. — We include under this head the 
numberless salts of the hydrocarbon radicals usually distin- 
guished as different kinds of ether. These bodies are, for the 
most part, volatile, and have an agreeable odor which resembles 
that of fresh fruit, and several of them are used by the confec- 
tioners as essences. They are produced by reactions similar 
to those employed in the preparation of metallic salts. 

CJTfCl + Ag-0-O,R,0 = AgCl + C 2 H f 0-O 2 W & 0. [462] 

Argentic Acetate. Acetic Ether. 

C 2 H 5 -0-Na+ C<H 7 0-Cl=iNaCl+ C 2 H,-0-C,H 7 0. [463] 

Butyrylic Chloride. Butyric Ether. 

H, o 5 ff n = 2 =S0 2 + K-0- G 2 H, = 

Potassic Acetate. 

B,K=OfS0 2 + C 5 H n -0-C 2 H z O. [464] 

Amylic Acetate. 

C 2 H f O-H+ H'0-G 2 H z O = C 2 H--0-C 2 H z O -f H.,0. [465] 

In reactions like the last, when a weak acid is unable by it- 
self to produce the decomposition of the alcohol, the presence 
of a strong mineral acid will sometimes determine the forma- 
tion of the ether. The reaction is then best expressed as if in 



§446.] MONATOMIC COMPOUNDS. — MARSH GAS SERIES. 493 

C 2 H f O-H+ KfOfSO, = H,C 2 Hf0. f S0 2 + H 2 0. 
H, Q& 2 =S0 2 + H-0-C 7 H 5 = [466] 

Benzoic Acid. 

HfOfS0 2 -\- C 2 H f O-C 7 H 5 0. 

Benzoic Ether. 

C 4 ff d -0-H-\- HCl = CJfrCl + H 2 0. 

[467] 
C 4 H 9 -Cl + HO-CHO = HOI + C 4 H,-0-CHO. 

When acted on by strong alkaline bases the compound ethers 
yield a metallic salt and an alcohol. 

C 2 H f O- C 2 ff 3 O + K- 0-H= K-0-C 2 H 3 + C 2 H 5 0-H. [468] 

Since the ethers are quite insoluble in water, such reactions are 
best obtained in alcoholic solutions, and this kind of decomposi- 
tion is frequently called saponification. At a high temperature 
the ethers may be saponified by water alone. 

445. Anhydrides. — The simple and mixed ethers are anhy- 
drides, but the name is usually confined to the oxides of the 
acid radicals. Acetic anhydride may be obtained by the fol- 
lowing reaction, 

K-0-C 2 ff 3 + C 2 ff 3 0-Cl = KCl+(C 2 H 3 0) 2 =0, [469] 

and propionic, butyric, and valerianic anhydrides may all be 
prepared in a similar way. Formic anhydride, however, has 
not as yet been formed. In contact with water these anhy- 
drides dissolve only slowly, in measure, as they are converted 
into the corresponding acids. 

446. Haloid Ethers. — The term haloid means resembling 
common salt, and is applied to those compounds which, like 
salt, are formed after the simple type of HCl, and includes the 
cyanides, chlorides, bromides, &c, of the hydrocarbon radicals. 
These ether-like bodies are formed in a great variety of re- 
actions. 

C 2 H 5 - 0-H+ HCl = C 2 H 5 - CI + H 2 0. [470] 

3 C 5 H 1]r O-H+ PCl 3 = BfOfPOH+ 3 C 5 H lf Cl. [471] 

5C 2 H f O-H+I 5 + P=HfOfPO+5C 2 H 5 -I-\- H 2 0. [472] 

CH 4 + CI- CI == CJTf CI + H- CI [473] 



494 ALCOHOLS AND THEIR DERIVATIVES. [§447. 

When acted on by an alcoholic solution of potash, all the 
haloid ethers, except the cyanides, are converted into alcohols. 

c 5 n L1 - ci + k- o-n= kci + c 5 h u -o-k [474] 

The reaction of the cyanides has already been given [444]. 

The haloid ethers are allied to the hydrogen acids, and like 
these combine with ammonia, and by the action of potash on 
the salts thus formed various amines may be obtained. 

NH 3 + C 2 ff 5 -I= (mCAHs)-L 

[4751 
(M C,JI 5 ,JI 3 yi+ K-0-H= KI+ ff 2 + H 2 . C 2 H 5 -K 

Ethylamine. 

Ethylic iodide, heated in a sealed tube with water, is con- 
verted into common ether. 

2 C 2 H 5 I+ R f O=( C 2 H 5 )fO + 2HL [476] 

Methylic chloride, when acted on by chlorine, yields the fol- 
lowing substitution products, and it will be noticed that the 
boiling-point increases in proportion as the atoms of hydrogen 
are replaced. 

B. P. b. p. B. p. b p. 

CllfCl —21°, CH 2 Cl 2 31°, CHCk 60°.8, CCl A 78°. 

The compound CHCl z is called chloroform, and is an anaes- 
thetic agent made in large quantities by heating alcohol or wood 
spirit (methylic alcohol) with a solution of chloride of lime 
(282). When boiled with an alcoholic solution of potash, chlo- 
roform is converted into potassic formiate, and chlorine gas, 
under the influence of sunlight, changes it into carbonic chloride. 

CHCl 3 +4;K-0-n~=3KCl-\-K-0-(CO-I{)+2H 2 0. [477] 

Bromoform, CJTBr 3 , and Iodoform, CHI 3 , are also known. 

447. Aldehydes. — These bodies, already mentioned as the 
products of the imperfect oxidation of the alcohols [442], may 
also be obtained by distilling a mixture of potassic formate with 
the potassic salt of the acid corresponding to the aldehyde re- 
quired. 

K-O-(CO-H) + K-0-(CO-CH 3 ) = 

KfOi-CO + H-(CO-CH 3 ). [478] 

Acetic Aldehyde. 



§ 448.] MONATOMIC COMPOUNDS. — MAESH GAS SERIES. 495 

The aldehydes are distinguished by a strong affinity for oxy- 
gen. They not only absorb oxygen gas from the air, but they 
reduce argentic oxide, and when heated with alkaline hydrates 
they evolve hydrogen, passing in each case into the correspond- 
ing acid. 

B-(O0-OII 3 ) + = H-0-(CO-CH A ). [479] 

Aldehyde. Acetic Acid. 

fi-(CO-Cff 3 ) + Ag a O = H-0-{CO-CH,) + Ag-Ag. [480] 

H-(CO-CH 3 ) + K-0-H= K-0-(CO-CII 3 ) + H-H. [481] 

By nascent hydrogen (water and sodium amalgam) the alde- 
hydes are converted back into alcohol. 

H-{GO-GH 3 ) -f H-H= C 2 H--0-H. [482] 

Most of them yield crystalline compounds with ammonia. 

H-{ CO-GH 3 ) -f NH 3 = NH±{ CO-CH*). [483] 

So also by dissolving potassium in aldehyde we obtain the 
reaction 

2H-(CO-CH 3 ) -f K-K= 2K-(O0-OH 3 ) + H-R [484] 

The aldehydes are named after the corresponding acids. 
The first is formic aldehyde H-(CChH), and the seven succeed- 
ing terms of the same series have been obtained. Of acetic 
aldehydes there are three polymeric modifications. The nor- 
mal compound is a very volatile liquid, boiling at 21° and hav- 
ing a strong suffocating odor. 

448. Ketones. — This name is applied to a class of com- 
pounds outwardly resembling the alcohols and having a pleas- 
ant ethereal odor. They are isomeric with the aldehydes, but 
differ from them widely in their chemical relations, for they are 
comparatively inactive bodies, and show no tendency to unite 
with oxygen. They are most readily obtained by distilling the 
potassic or calcic salts of the monatomic acids. 

Ga-0 2 =(GO-GB 3 ) 2 = Ga-0 2 =GO + {GH 3 ) 2 =GO. [485] 

Calcic Acetate. Acetone. 

Ca=0 2 =(GO-G 2 IT 5 ) 2 = Ga=0 2 =GO + (G 2 ff 5 ) 2 =GO. [486] 

Calcic Propionate. Propione. 



496 ALCOHOLS AND THEIR DERIVATIVES. [§449. 

It will be noticed that the two ketones thus obtained differ 
by 2 CH 2 , although the initial acids ouly differ by CH 2 ; but by dis- 
tilling an intimate mixture of the two salts we can obtain the 
intermediate term of the series, namely, CH s ,C 2 H 5 = CO. 

Ketones can also be obtained by acting on acetyl chloride or 
its homologues with zinc methide or ethide. 

2(CK d -CO)-Cl+ Z,i={CH 3 ) 2 = ZnCI a + 2(CH 3 ) 2 =CO. [487] 

Moreover, they have been formed by the action of carbonic 
oxide on sodic ethide and the homologous compounds. 

2Na-C 2 H 5 -\-CO = Na-Na + {C 2 H 6 ) 2 -CO. [488] 

449. Pseudo-Alcohols. — By the action of nascent hydrogen 
the ketones are converted into compounds isomeric, but not 
identical with the alcohols. 

( CE^f CO + HH= ( CH 3 ) 2 - CH-Ho. [489] 

The bodies of this class are also called secondary alcohols, 
and are distinguished by the prefix iso. Their relations to the 
normal alcohols are illustrated by the following symbols : — 

(CH 3 -CH)-Ho, {CH 3 CO)-H, (CH f CO)-Ho, 

Lthylic Alcohol. Aldehyde. Acetic Acid. 

{& 2 H f Om-&>, (C 2 H f COyH, {C 2 H f CO)-Ho, 

Propylic Alcohol. Aldehyde. Propionic Acid. 

( CH,) 2 = CH-Ho, ( CH S ). 2 = CO. 

Isopropylic Alcohol. Acetone. 

As common alcohol passes by oxidation first into aldehyde 
and then into acetic acid so normal propylic alcohol, when 
oxidized, yields similar products. But under the same con- 
ditions the isopropylic alcohol gives acetone, which, although 
isomeric with propionic aldehyde, cannot be converted by fur- 
ther oxidation into propionic acid, and it is evident that such a 
change would not be possible without a complete remodelling 
of the molecule. The difference between these isomeric alco- 
hols, indicated by their reactions, is still further manifested in 
their boiling-points, since while the normal alcohol boils at 96°, 
the pseudo-alcohol boils at 87°. Besides the isopropylic two 
other pseudo-alcohols have been obtained which probably be- 
long to the same class. 



§451.] MONATOMIC COMPOUNDS. — VINYL SERIES. 497 

Isoamylic Alcohol ( CH Z , G*Hf CH)-Bo, 

Isohexylic Alcohol ( CH Z , C^Hf GH)-Ho. 

Lastly a pseudo-alcohol has been discovered, isomeric with 
butylic alcohol, which appears to be constituted after still a 
thiid type, and to be the first of a class of tertiary alcohols. 

Pseudo-butylic Alcohol (CH 3 )fC-Ho. 

If we represent by U any univalent hydrocarbon-radical, the 
general symbols of the three classes of alcohols we have dis- 
tinguished would be as follows : — 

M-CHfHo, %fCH-Ho, ^O-Ho. 

Primary Alcohol. Secondary Alcohol. Tertiary Alcohol. 



2. Vinyl Series. 

450. Vinyllc Alcohol. — Acetylene like ethylene dissolves in 
sulphuric acid, and when the product is distilled with water we 
obtain the hydrate of the radical vinyl or vinylic alcohol. 

BfOfSO, + C 2 H 2 = H,C 2 HfOfS0 2 . 

[490] 
%C 2 ff 3 =OfS0 2 ±H-0-II=lT<f0.fS0 2 + C 2 H z -0-H. 

This alcohol is isomeric both with acetic aldehyde and the 
oxide of ethylene. 

C 2 H,- OH, ( Cff s - CO)-H, C 2 H A = 0. 

Vinylic Alcohol. Acetic Aldehyde. Ethylenic Oxide. 

No acid has been obtained from it by the action of oxidizing 
agents. 

451. Alhjllc Alcohol. — The second term of the vinyl series 
may be formed from glycerine by the following reactions. 

Glycerine. 2 C,ff f I + 2H 2 =0 2 =POH + II [491] 

Allylic Iodide. 

2C 3 H f I+ Aa 2 -0 2 -C 2 2 = 2AgI+ {C z H,) 2 =0 2 ^C 2 2 . [492] 

Argentic Oxalate. Allylic Oxalate. 

(<ZB 5 )fOfC 2 2 + 2ff 3 2?= 

(H 2 N~)fC 2 2 -\- 2C,U 5 -0-ff. [493] 

Oxamide. Allylic Alcohol. 

RF 



498 ALCOHOLS AND THEIR DERIVATIVES. [§452. 

When dehydrated by phosphoric anhydride (184) this alcohol 
gives allylene the second member of the acetylene series. 

( CA)-0-H- H 2 = C 3 H 4 . [494] 

Oil of garlic is the sulphide of allyl ( C 3 H d ) 2 =S and oil of 
mustard the sulphocyanate 3 H 5 -S~CN. 

When acted on by oxidizing agents, allylic alcohol yields 
both an aldehyde and an acid, and the following symbols indi- 
cate the relations and probable constitution of the three bodies. 

( GRf OH- CH 2 )-Ho, ( Cfff OH- CO)-H, ( OH/ OH- 00)-Ho. 

Allylic Alcohol. Acrolein (Aldehyde;. Acrylic Acid. 

452. Acrolein is formed abundantly during the dry distil- 
lation of fats or similar glycerides (474). and the pungent odor 
of its vapor, so intensely irritating to the eyes, is familiar to 
every one. It may be best procured by the action of dehy- 
drating agents, such a-; phosphoric anhydride or sulphuric acid, 
on glycerine, from which it differs by 2H 2 0. 

(OH 2 OHCH 2 yHo 3 —2H 2 0= {OH 2 -CH-CO)-R [495] 

Glycerine. Acrolein. 

453. Acrylic or Oleic Series of Acids. — Acrylic acid is the 
first member of a large and important series of acids, which 
are associated with the acids of the acetic series in the natural 
fats and oils. Only those members of the series are included 
in the following list which we have reason to believe are con- 
stituted like acrylic acid. Of the constitution of the other fat 
acids of this class we have as yet no knowledge. 

Acrylic Acid 3 H 4 2 or Ho-(00 OH-0 H 2 ), 

CrotonicAcid 4 H,0 2 " Ho-(00-OH=C 2 H 4 ), 

Angelic Acid 5 H S 2 " Ho-(CO-CH=0 3 H 6 ), 

Pyroterbic Acid O 6 H 10 2 « Ho-( CO- OH- 4 H 8 ), 

Oleic Acid 1& H 34 2 " Ho-{00-OH-0 16 H 32 ). 

These acids are closely allied to those of the acetic series. 
Acrylic acid under the influence of nascent hydrogen changes 
into propionic acid, and when acted on by bromine it yields a 
simple derivative of the same compound. 



§454.] MONATOMIC COMPOUNDS. — VINYL SERIES. 499 

Ho-(GO-GH-GH 2 ) + H-H= Ho-(CO-C 2 H,). 

[496] 
Ho-(GO-CHGH 2 ) + Br-Br = Ho-(GO-G 2 H 3 Br 2 ). 

Moreover, when heated with caustic potash all the acids of 
the above list break up into two acids of the acetic series, one 
of which is always acetic acid itself. 

Ho-(GO-GHCH 2 ) + 2K-0-U= 

Ko\GO-GH 3 ) -f Ko-(CO-H) + H-H. [497] 

Ho-(CO-CHG 2 H 4 ) + 2KOH= 

Ko-(GO-GH 3 ) + Ko-(GO-GH.) -f- H-H. [498] 

Ho-(CO-CH-C 3 HS) -f 2K-OH = 

Ko-(CO-CH s ) -f Ko-(CO-C 2 H 5 ) + #"-.# [499] 

Ho-{GO-CHC,H s ) -f 2K-0-H= 

Ko-(CO-CH 3 ) -f Ko-{00-C :i H 7 ) -f ## [500] 

Ho-{GO-CH-G m H 3 . 2 ) -f 2K-0-H^= 

Ko-{GO-GH 3 ) + Ko-(GO-G 15 H 3l ) + J7-tf [501] 

Salt of Palmitic Acid. 

The alkali appears to act on the defines (430), assumed to 
exist in the radicals of these compounds, and replaces them 
with iZj, thus forming acetic acid in every case, while at the 
same time it converts the define itself into another acid of the 
acetic series. 

454. Secondary Acids. — Acids isomeric with those of the 
acrylic series have been obtained by means of reactions which 
indicate the structure of the resulting molecules, and a com- 
parison of the reactions of these artificial products with those 
of the normal acids shows that the rational symbols we have 
assigned to the latter must be essentially correct. The sym- 
bol of oxalic ether may be written Et-0-{CO-GO)-0-Et, 
and there are good reasons for writing the symbols of the 
zinc compounds of the monad radicals (324) thus, (Zn^)-^, 
indicating, as is undoubtedly the case, that the group (Zn${)- 
acts as a monad radical. When now a body of this class acts 
on oxalic ether, the following reaction takes place : — 

Et-0-{CO-GO)-0-Et + 2(^H)"H = 

Et-0-(GO-Cn 2 )-0-(Zn$) -{- Et-O-(Znn). [502] 



500 ALCOHOLS AND THEIK DERIVATIVES. [§455. 

If next water is added, the product of the last reaction 
undergoes a still further change, 

M-0-(CQ~CU 2 )-0-(Zn&) + 2H 2 = 

Za-0 2 -H 2 + BU + Et-0(CO~CK 2 )-0-H, [503] 

and the whole effect, as will be seen, is to replace one atom of 
oxygen in the radical of oxalic acid with two atoms of a radical 
of the methyl series. Lastly, if we subject one of these acids, 
thus synthetically obtained, to a dehydrating agent (PCl 3 or 
P 2 O d ), the result is an isomer of the acrylic series. 

M-,0-(CO-C$ 2 yO-H— H 2 = JSt-0-(CO-C&<W). [504] 

Here 3* stands for a dyad radical of the olefiant series, and 
the symbols of the compounds which have been obtained in 
this way are given below. By comparing these with the 
symbols of the normal isomers, the difference of structure will 
be evident. 

Secondary Acids. Normal Acids. 

Methyl-acrylic Acid H*fr(CO-C(CH a yCH 3 ) H-0-(CO-CH=CJIJ 
Methyl-crotonic " H-0\CO-C{CH z )--C 3 U^ H'0-(CO-CH=C,H 6 ) 
Ethyhcrotonic " H-0-\cO-cic % H 6 yC t lQ H-O-iCO-CH^H,) 

When treated with potash, the secondary acids break up like 
the normal compounds, but they only give acetic acid when the 
dyad radical is ethylene, and after writing these reactions, ac- 
cording to the models given above, it will be seen not only that 
these facts confirm the opinion already expressed in regard to 
the nature of the change, but also that the close coincidence be- 
tween theory and observation gives strong grounds for believing 
that we have gained positive knowledge in regard to the 
structure of the bodies we have been studying. 

455. Tertiary Acids. — By means of the following reaction 
a second isomer of crotonic acid has been obtained, which must 
have a structure differing from either of the other two condi- 
tions of this compound. Compare [444]. 

(CHfCH-CH 2 )-CN+ K-0-R+ H 2 =s 

Allylic Cyanide. (CBfCH-CB a -COyO-K+M%. [505] 

Potassic /J Crotonate. . 



§457.] MONATOMIC COMPOUNDS.— -PHENYL SERIES. 501 



3. Phenyl Series. 

456. Benzoic Alcohol. — If the peculiar grouping of the 
carbon atoms represented in Fig. c (428) is an essential char- 
acter in the structure of the radical phenyl and its homologues, 
it is obvious that the lowest normal alcohol of this series, formed 
after the type of common alcohol, must have the composition 
represented by the symbol (C G II 5 -CJI 2 y0-JI. This body is 
Benzoic Alcohol, and the corresponding aldehyde and acid are 
the well-known compounds Oil of Bitter Almonds and Benzoic 
Acid. 

( c 6 ff 5 - ch,yo-h, ( c 6 ff f ooyir, ( cys- coy ok 

Benzoic Alcohol. Oil of Bitter Almonds. Benzoic Acid. 

Benzoic alcohol may be prepared by treating oil of bitter 
almonds with an alcoholic solution of potassic hydrate. 

2(c,B^-ooyii-y KO-R= 

(0 6 ff f CO)-0-K+ (C 6 ITfGff 2 yO-K 

It may also be made from toluol (methyl-phenylic hydride) 
(434). " 

O e H f Off s + 01-01= (OsfffCftyCl+HCl. 

Toluol. Toluic Chloride. 

(C 6 H f CH 2 yCl + K-0-H= KCl + ( C 6 ff f CH 2 )- O-K 

Moreover, benzoic acid, when acted on by nascent hydrogen, 
is reduced in part, first to benzoic aldehyde (oil of bitter al- 
monds), and then to benzoic alcohol. 

The essential oil of cumin is a mixture of cymol, O 10 II w and 
cuminic aldehyde, from which may be derived on the one side 
cumylic alcohol homologous with benzoic alcohol and on the 
other cuminic acid homologous with benzoic acid. 

(C 9 ff n -CR 2 )-0-ff, (C 9 HnCO)-H, (C,ff n -CO)-0-K 

Cumylic Alcohol. Cuminic Aldehyde. Cuminic Acid. 

Sycocerylic alcohol {C^H^-CH^-O-H^ obtained from a resin 
brought from New South Wales, is supposed to be another 
member of this series. 

457. Phenols. — By comparing the symbols of the normal 
alcohols, of either class, as given above, or still better when 



502 ALCOHOLS AND THEIR DERIVATIVES. [§457. 

exhibited by one of the graphic methods, the student will see 
that the peculiarity in their structure consists mainly in the cir- 
cumstance that two atoms of hydrogen are attached to the 
same carbon atom, to which the atom of hydroxyl is also united, 
so that when these atoms of hydrogen are replaced by an atom 
of oxygen, the radical oxatyl H-Q-CO- is formed in the mole- 
cule, and this, as has been shown, appears to be the acidifying 
principle of all the organic acids. Hence by a very simple re- 
placement, which does not alter the molecular structure, the 
alcohol changes into an acid. 

Such now is the structure of benzoic alcohol, but such would 
not be the condition if the Ho were united directly to one of 
the carbon atoms, which form the nucleus of the radical 
phenyl, and it can easily be seen that the resulting product, 
C 6 HfO-H, could not change into an acid, at least of the oxatyl 
type, without disturbing the peculiar atomic grouping shown in 
Fig. c (428). Compounds thus constituted are called Phenols. 

The compound C&HfO'His a well-known commercial pro- 
duct, called carbolic acid. The more appropriate name is 
phenylic alcohol, since it is a secondary or pseudo-alcohol of the 
phenyl series, differing from the true alcohols in that it does not 
yield by oxidation a homologue of benzoic acid. As we might 
expect, however, the different hydrogen atoms of the radical 
may be replaced by CI, Br, or N0 2 , and a great number of 
substitution products may be thus obtained, of which the best 
known is the so-called Picric Acid (C C) H 2 {N0 2 ) 3 )-0-H 

Phenylic alcohol is one of the products of the dry distillation 
of coal, and it is procured for the arts, from the coal-tar of the 
gas-works. It may also be formed by distilling salicylic acid 
with baryta or lime, or by the action of nitrous acid on aniline 
(167). ' 

H-0( CO-a,.H t )-0-H-\- CaO— CJJ K 0-H+ Ca--OfCO. 

Salicylic Acid. Phenylic Alcohol. 

[506] 
H 2 , C«HfN '+ H-O-NO = C G H f O-H-\- H 2 + N-N. 

Aniline. Nitrous Acid. 

Phenylic alcohol smells like wood-tar creosote, and is an 
equally powerful antiseptic agent. Indeed, it constitutes the 
greater part of the so-called coal-tar creosote. There is some- 
times associated with it a small quantity of an homologous com- 



§458.] MONATOMIC COMPOUNDS. — PHENYL SERIES. 503 

pound, which has been named cresylic alcohol, and this is the 
only other phenol which has as yet been obtained. It closely 
resembles the first, has the symbol C 7 II 7 -0-If, and is therefore 
isomeric wilh benzoic alcohol. The student should seek to 
exhibit by graphic symbols the difference in the structure of 
these two isomeric compounds, on which the wide differences in 
their properties and chemical relations depend, and thus show 
also why a normal alcohol isomeric with phenylic alcohol can- 
not be produced. 

■458. Acids of the Phenyl Series. — Benzoic acid, formerly 
exclusively obtained by sublimation from gum benzoin, is now 
more frequently procured from hippuric acid (1G8), which is 
found abundantly in the urine of herbivorous animals. When 
hippuric acid is boiled with hydrochloric acid, the radical ben- 
zoyl (C 7 H 5 0) iii this amide changes place with If of If- OH, 
and the products are glycocol and benzoic acid. Only two 
other acids of this series are known. The normal series proba- 
bly includes 

Benzoic Acid II-0-{C0-0,H 6 \ 

Toluylic Acid H-0-{CO-C 7 H 7 ) or ff-0( CO- C.IIfCIf), 

CuminicAcid H-0-(CO-C»H n ) or H-0-{CO-C^-C d H 7 ). 

This class of compounds has been comparatively little studied, 
and future investigation will probably bring to light not only 
other members of the series, but also other series of related 
acids, differing from the normal compounds by peculiarities of 
structure or slight variations in composition. One such com- 
pound is already known, and this bears the same relation to 
benzoic acid that crotonic acid bears to acetic acid, 

ff-O(CO-Cffz), II-0-(CO-CIf=C 2 If 4 ), 

Acetic Acid. Crotonic Acid. 

H-0-(C0-O 6 H 6 ), H-0-(CO-C G H ?r C 2 H,) ; 

Benzoic Acid. Cinnamic Acid. 

and when heated with potassic hydrate cinnamic acid breaks up 
into benzoic and acetic acids, thus : — 

H-0-{CO-C & H^C 2 H,) + 2K-0-If= 

K-0-(CO-C G H 5 ) + K-0\GO-CH z ) + H-H. [507] 



504 ALCOHOLS AND THEIR DERIVATIVES. [§459. 

Salicylic acid is another compound belonging to the phenyl 
group, and its relation to benzoic acid is indicated below. The 
volatile oil of meadow-sweet (Spircea ulmaria) is supposed to 
be the aldehyde of this acid, and the oil of wintergreen, called 
also chequer-berry ( Gaultheria procumbens), is methyl salicylic 
acid. 

H-0-(CO-C Q H 5 ), H-0-(CO-C«H 4 yO-H, 

Benzoic Acid. Salicylic Acid. 

b-(co-c«h 4 )-o-ii, h- o-{CO-c (i ff 4 )-o-cir 3 . 

Oil of Meadow-sweet. Oil of Wintergreen. 

These compounds, however, being diatomic, more properly 
belong under the next head. 



DIATOMIC COMPOUNDS. 

459. Glycols. — The dyad radicals of the ethylene series 
may combine with two atoms of hydroxyl, and the diatomic 
hydrates thus formed constitute an interesting class of alcohols 
which are usually called glycols, and whose relations to the 
water-type have been already explained (41). The following 
reactions illustrate three of the methods by which these bodies 
may be produced : — 

1. C 2 H 4 + Br-Br = C 2 H 4 -Br 2 . [508] 

2. C 2 ff 4 =Br 2 + 2Ag-0-C 2 H 3 = 

2AgBr + G 2 H 4 -0 2 -{C 2 H z G) 2 . [509] 

3. C 2 ff 4 = 2 =( C 2 H Z 0) 2 + 2K-0-H= 

Diacetic Glycol. 2K~0-{C 2 H,0) + C 2 HfOfH 2 . [510] 

Ethyl Glycol. 

1. C 2 H 4 -\-H-0-Cl = C 2 H{Ho,CL [511] 

Monochlorhydrine of Glycol. 

2. C 2 H 4 -Ho, Cl+ Ag-O- C 2 ff 3 = 

A 9 Cl + C 2 fff0 2 =(C 2 ff 3 0),K [512] 

3. c 2 ff 4 =o 2 =(c 2 ir,o),if-\-K-o-ir= 

Mono-acetic Glycol. K-0~C 2 H,0 + C 2 H 4 =OfH 2 . [513] 

Ethyl Glycol. 

CJffHb 2 ,Cl -f H-H= HCI+ C ? H^0 2 -H 2 . [514] 

Monochlorhydrine of Glycerine. Propyl Glycol. 

The normal glycols, like all normal alcohols, are easily oxi- 



460.] DIATOMIC COMPOUNDS. 505 

dized, and on account of their diatomic nature a reaction simi- 
lar to [442] may be once repeated with each of these bodies. 
Every such glycol thus yields two acids, whose relations may 
be best indicated by writing the symbols as below : — 

H-0-{CH 2 CH 2 )-0-H, 

Eihylic Glycol. 

H-0-(CO-CH^)-0-H, 

Glycollic Acid. 

H-0-(CO-CO)-0-H y 

Oxalic Acid. 

H-0-(CK 2 CH 2 CH 2 )-0-H, 

Propylic Glycol. 

H-0-{CO-CH 2 -CH,)-0-H, 

Paralactic Acid. 

H-0-(CO-CE 2 CO)-0-H, 

Malonic Acid. 

H-0-{CR 2 -C,ff 4 -CR 2 )-0-H, 

Butylic Glycol. 

H-0-(CO-0 2 ff 4 -CB 2 )-0-II, 

JI-0-{COC 2 R 4 -COyO-IL 

Succinic Acid. 

In these symbols those hydrogen atoms which are associated 
with CO are strongly basic, and those which are associated 
with CH 2 , although also typical and replaceable under certain 
conditions, cannot be displaced by the usual metathefical meth- 
ods (21). Iu this we find the explanation of the fact stated 
in (41), that the acids homologous with g-lyeollic acid are only 
monobasic, although diatomic and the acids homologous with 
oxalic acid, both dibasic and diatomic. Of the glycols included 
in the list given in the section just referred to only the first is 
supposed to have the constitution exhibited above. It is prob- 
able that in the others the atoms are differently arranged. 

The following derivatives of ethylic glycol will further illus- 
trate the chemical relations of this class of compounds : — 

Cyanhydrine CMfHo. CJV, 

Bromhydrine C 2 HfHo,Br, I 

Dibromhvdrine (ethylene dibromide) C 2 fffBr 2 , 
Bromo-ethylic Glycol 2 ff 4 =( C 2 ff 5 ) 0,Br, 

Sulphur Glycol ' C 2 HfS 2 =H 2 . 

Compare also the products of [509]. [511], and [512]. 
460. Ethylenic Oxide or Ether, which has already been 
mentioned as isomeric with both vinylic alcohol and acetic 
22 



506 ALCOHOLS AND THEIR DERIVATIVES. [§461. 

aldehyde, is another of the derivatives of ethylic glycol. It 
may be produced thus : — 

C 2 HfOfH 2 + HGl = C 2 HfHo,Cl + B 2 0. 

[515] 
C 2 H 4 =Ro, CI + K- 0-H= C 2 B 4 = + B 2 + KCl. 

Ethylenic Oxide. 

The following reactions illustrate the remarkable relations 
of this compound : — 

C 2 H 4 -0 + R-B z= C 2 B 5 -0-B. [51 6] 

C 2 B 4 =0 + 0-0 = H-0-(CO-CH 2 )-0-K [517] 

G 2 Ef + B-Cl = C 2 B 4 =Bo, 01. [518] 

C 2 B 4 - + H 2 0— C 2 B 4 - 2 =B 2 . [5 1 9] 

It precipitates many oxides from solutions of their salts. 

MgCl 2 + 2C 2 B 4 -0 + 2B 2 = 

2 C 2 B 4 -Bo, CI + Mg-OfH 2 . [520] 

By expressing these reactions in a graphic form the student 
will see that they are all possible without a disruption of the 
original molecule, and this accounts for the great difference 
between the behavior of ethylenic oxide and that of ethylic 
ether, which in other respects is similarly constituted. 

461. Condensed Glycols. — The peculiar constitution of 
ethylenic oxide, just referred to, gives rise to a class of glycols 
in which the basic radical consists of two or more atoms of 
ethylene soldered together by atoms of oxygen (38). Thus, 
representing ethylene by Et = G 2 H 4 , we have, 

Glycol Et~-0 2 =B 2 , 

Diethylenic Glycol (Et-0-Et)=OfB 2 , 
Triethylenic Glycol (Et-0-Et-0-Et)=0 2 =B 2 , 
Tetrethylenic Glycol (Et-O-Et-O-Et-O-Et)-OfB^ 
Pentethylenic Glycol {Et-0-Et-0-Et-0-Et-0-Et)=OfB 2 < 
Hexethylenic Glycol (El-0-Et-0-Et-0-Et-0-Et-OEt)-0 2 =B 2 . 

These bodies are formed by direct synthesis when glycol and 
ethylenic oxide are heated together for many dnys in sealed 
tubes, but they are more readily produced by the following 
reactions : — 

C 2 B 4 -Br 2 + G 2 Hi-Ho 2 = 2 C 2 B 4 -Bo,Br, [521] 






§462.] DIATOMIC COMPOUNDS. 507 

C 2 ff 4 =Bo,Br + C 2 H 4 =Ho 2 =(C 2 H 4 0-C 2 H 4 )-Ho 2 -\-H-Br, [522] 

C 2 ff 4 =fio,Br + ( C 2 H 4 OC 2 H 4 )=Ho 2 = 

(C 2 H 4 0-C 2 H 4 0-C 2 H 4 )-Ho 2 -\-HBr, [523] 
and so on. 

The last reactions are also obtained by heating together the 
original factors in closed tubes. The several changes succeed 
each other, and thus more and more complex molecules are 
gradually built up. However great the condensation, these 
condensed molecules contain but two typical atoms of hydro- 
gen, and when oxidized only four of the H atoms in the radi- 
cal can be replaced with oxygen as in the normal glycol. At 
least this is true of diethylenic and triethylenic glycol, and with 
these alone the reactions have been studied. The symbols of 
the acids resulting from the oxidation in the two cases may be 
written, 

( G 2 H 4 0- C 2 2 )= 2 =& 2 , and ( C 2 H 4 - - G 2 H 4 - C 2 2 )= 2 =IT 2 . 

The compound (C 2 ff 4 -0-C 2 H 4 ) = 2 is also known, and these 
remarkable bodies derive a special interest from the fact that 
the study of the phenomena which they present has furnished 
the key to the explanation of the more complex phenomena of 
the same kind with which we are already familiar in the min- 
eral kingdom. 

462. Monobasic Acids. 1. Lactic Family. — This family of 
acids, which represents the first stage in the oxidation of the 
glycols, is at the present time especially interesting, because the 
phenomena of isomeri-m have been here studied with more 
success than in any other class of compounds of equal com- 
plexity. According to our view, the normal glycol is one 
which admits of two degrees of oxidation, as represented in 
(459). Such a glycol may be represented by the general 
symbol Ho-( CH 2 ( CH 2 ) n -CH 2 \Ho, where ( CH 2 ) n stands for any 
define, and common glycol is the first term of the series, for 
which n = o. The glycols actually known, however, with the 
exception of the first, belong to a different type, represented by 
the symbol Ho-{CH 2 CH\X)-ffo, in which fj stands for a radi- 
cal of the methyl series, and which is capable of variation, 
not only by changing this radical, but also, as in the normal 
series, by the addition of (CH 2 ) n between the two carbon atoms 



508 ALCOHOLS AND THEIR DERIVATIVES. [§463. 

of the original type. Moreover, it is evident that we might 
have still a third class of glycols corresponding to the general 
symbol Ho -( CH,-( GH 2 ) n - G%)-Ho. 

From these three classes of glycols we should evidently ob- 
tain, at the first stage of oxidation, three classes of acids, thus : — 

Normal. Secondary. Tertiary. 

Ho-(CO-CH 2 )-Ho, Ho-(GO-GH$)-Ho, Bo-(CO-C% 2 )-JIo ; 

Normal Olefine. 

Ho -(CO-{ GH 2 ) n - GH 2 )-Ho, 

Secondary Olefine. 

Ho-(GO-( GH 2 ) n - GH§)-Ho, 

Tertiary Olefine. 

JIo-(GO-{GII 2 ) H -Gi%)-IIo; 

and the term olefine may be appropriately used to distinguish 
the succeeding members of each series from the first. More- 
over, it is equally evident that by replacing with univalent 
radicals the hydrogen of the non-basic hydroxyl we may 
obtain a whole group of acids corresponding to each of the 
members of the above scheme. These last acids we shall call 
etheric, and we will next endeavor to show that the symbols 
which have been assigned to the known members of the lactic 
family of acids are legitimately deduced from observed facts. 

463. Normal Acids. — Only three members of this series 
are known. 

Glycollic Acid Ho-(GO-GH 2 )-Ho, 

Paralactic Acid Hu-(GO-GH 2 GH 2 )-Ho, 

Paraleucic Acid Ho\GO\GH 2 )/GH 2 )-Ho. 

The symbol of glycollic acid may be inferred from that of 
glycol, since the acid is a product of the direct oxidation of this 
diatomic alcohol. The symbol of paralactic acid may be re- 
ferred back to that of ethylene, which we assume to be 
(GH 2 =GH 2 ), by means of the following reactions : — 

1 . ( GH$ GH 2 ) + GO Gl 2 = Gl-{GO- GH 2 - GH 2 )- Gl 

2. Gl-(GO-GH 2 -GH 2 )-Gl+3KHo= [524] 

j8 Chloropropionylic Chloride. 

Ko(GO-GH 2 GH 2 )-Ho + 2KGI + H 2 0. 

Potassic Paralactate. 



§464] DIATOMIC COMPOUNDS. 509 

So abo 

CN-(CH 2 -CH 2 )-Ho + KHo -f H 2 = 

Cyanhydriue. Rq _ ( QQ.Qjfr CRfrHo + NH & . [525] 

Potassic Paralactate. 

The body called paraleucic acid was formed by reactions simi- 
lar to [524], using amylene instead of ethylene, but it has not 
yet been completely investigated. 

464. Secondary Acids — This series includes the most im- 
portant acids of the lactic family, and corresponds to the series 
of known glycols. For this reason its members are regarded 
by Frankland as the normal compounds. The following are 
here classed : — 

Glycollic Acid Ho-{CO-CHH)Ho, 

Lactic Acid Ho-\GO-CHMt) x -Ho. 

Oxybutyric Acid Ho-(CO-<3HEt) x -Ho, 

Valerolactic Acid Ho\ GO-CHPrf-Ho, 

Leucic Acid Ho\cO-CHBafHo. 

Glycollic acid may be regarded as belonging to both the nor- 
mal and secondary series. Under certain conditions it is formed 
in the oxidation of common alcohol. 

2Ho-(CH 2 GH 2 H) +30=0 = 

Aicohoi. 2Ho-(GO-CH 2 )-Ho + 2H 2 0. [526] 

Glycollic Acid. 

The constitution of lactic acid is made evident by the follow- 
ing considerations. It has already been sliown that the symbol 
of aldehyde must be H-(CO-CH s ). When this is acted on by 
PC/ 5 we obtain a compound isomeric with ethylene chloride by 
the reaction 

H-(CO-CH z ) + PCl 5 = C! 2 =(CH-CIT 3 ) + POCl 3 . [527] 

Aldehyde. Ethylidene Chloride. 

This product, however, differs from ethylene chloride both 
in its physical and chemical properties, and it must therefore 
be the chloride of a distinct radical, to which has been given 
the name of ethylidene. Moreover, the mode of its production 
(190) leaves no doubt in regard to its constitution, and then by 

i M e = ( CE 3 )-, Et = ( C 2 H & )-, Pr = ( C 3 H 7 )-, Bu = ( C 4 # 9 )-. 



510 ALCOHOLS AND THEIR DERIVATIVES. [§465. 

exclusion we fix the symbol of ethylene as well ; for, as is 
evident, the atoms C 2 H^ to form a dyad radical, must be 
grouped in one or two ways, either 

-( CH 2 -CH 2 y, or =( CH-CH 3 ). 

Ethylene. Ethylidene. 

Now, as the cyanhydrine of ethylene yields paralactic acid, 
so the cyanhydrine of ethylidene yields common lactic acid. 

Ho, CN-{ CH-Me) -f K-Ho + H 2 = 

Cyanhydrine of Ethylidene. Ro\C 0~ CHMe\Ho + NH* [528] 

Salt of Lactic Acid. 

We can now interpret the following reaction by which lactic 
acid is obtained from propionic acid : — 

1. Ho-{ CO CH 2 CH S ) + CI- CI = 

Propionic Acid. Ho-(CO~ CHCl " CH 3 ) + HCL 

Chloropropionic Acid. T599T 

2. Ho-(CO-CHCl-Me) + 2KHo = 

Ko-{ CO-CHMe)-Ho + KCl + H 2 0. 

We are thus able to show to what part of the radical of 
propionic acid the hydrogen atom replaced by chlorine be- 
longed. Moreover, it is evident that the acid which would be 
obtained by the action of water on /3 chloropropionylic chloride 
(463) must differ from that formed as above, and we can under- 
stand the reason why. Lastly, since lactic acid has also been 
formed by the oxidation of propylic glycol, we conclude that 
the constitution of this body must be Ho-(CH 2 -CHMe)-Ho, as 
intimated in (462). 

For the methods by which the constitution of the other 
members of this series has been established we must refer 
the student to more extended works. The examples given 
are sufficient to illustrate the general course of the reasoning. 

465. Etheric Secondary Acids. — No secondary olefine acids 
are known, but by simple metathetical methods we can easily 
replace the hydrogen of the non-basic hydroxyl in the com- 
pounds of this series with various radicals, and the following 
bodies will serve as examples of the products thus obtained: — 

Methyl-glycollic Acid Ho -(CO- CH 2 )-Meo, 

Ethyl-lactic Acid Ho-( CO~CHMe)-Eto, 

Aceto-lactic Acid Ho -( CO-CHMe)-Aco> 

i Ac^-iCO-CTJ*). 



§469.] DIATOMIC COMPOUNDS. 511 

466. Tertiary Acids. — The following are known : — 

Dimethoxalic Acid Ho -( CO~CMe 2 )-Ho, 

Ethoraethoxalic Acid Ho-( CO-CMeEt)-Ho, 

Diethoxalic Acid Ho -( CO - CEt 2 )-Ho. 

Our knowledge of the constitution of these acids is based on 
the beautiful synthetical method (454) by which they were 
produced by Professor Frankland, who has also obtained 
etheric acids belonging to this division, but no corresponding 
olefines have been discovered. 

467. Isomerism in the Lactic Family. — The number of pos- 
sible isomeric combinations in this family of acids is evidently 
infinite. The following are two of the known examples : — 



Ho-(CO-CH 2 CH 2 )-Ho, 

Paralaciic Acid. 

Ho-{CO-CHMe)-Ho y 

Lactic Acid. 

Ho-(CO-CH 2 )-Meo, 

Methyl-glycollic Acid. 



Ho-(CO-CHFj)-Ho, 

Oxybutyric Aoid. 

Ho-(CO-CMe 2 )-Ho, 

Dimethoxalic Acid. 

Ho-(CO-CH 2 )-Eto. 

Eihyl-glycollic Acid. 



468. Lactic Acid is by far the most important member of 
the family to which it gives name, and one of the most common 
of the organic acids. It is the acid of sour milk and sauer- 
kraut, and is a general product of putrefactive fermentation. 
The acid contained in the gastric juice and many other animal 
fluids is said to be paralactic acid. The salts of laotic acid are 
very numerous, and those of the bivalent metals bind two 
atoms of the acid radicals. By the action of HI lactic acid 
may be converted into propionic acid. 

Ho-(CO-CH-Me)-Ho + 2HI= 

Lactic Acid. ' Ho-(CO-CH 2 -Me) J^H.O + I-I. [530] 

Propionic Acid. 

469. Monobasic Acids. 2. Pyruvic Series. — Two members 
only are well known : — 

Glyoxalic Acid Ho-(CO-CO)-H, 

Pyruvic Acid Ho -( CO - CO)- Me. 

The first may be regarded as the semi-aldehyde of oxalic acid, 
a compound called glyoxal being the full aldehyde, thus: — 

Ho-{CO-CO)-Ho, Ho-(CO-CO)-H, H-(CO-CO)-H. 

Oxalic Acid. Glyoxalic Acid. Glyoxal. 



512 ALCOHOLS AND THEIR DERIVATIVES. [§470. 

Both glyoxalic acid and glyoxal are formed when common 
alcohol is oxidized by nitric acid. 

Ho-(CH 2 -CH 3 ) + 3 = H-(CO-CO)-H+2H 2 0. 

Alcohol. Glyoxal. 

[531] 

jr-(CO-co)-a+ o — Ho-{co-co)-k 

Glyoxal. Glyoxalic Acid. 

Glyoxalic acid reduces argentic oxide like an aldehyde, and 
passes into oxalic acid. 

Ho-(CO-CO)-H + = Ho-(CO-CO)-Ho. [532] 

Glyoxalic Acid. Oxalic Acid. 

Compare (479). 

The relations of these compounds to the acids of the lactic 
family are equally close. 

Ho-(CO-CO)-H+ H-H= Ho-(CO-CH)-Ho. 

Glyoxalic Acid. Glycollic Acid. 

[533] 
Ho -(00 -CO)- Me + HH= Ho-(CO-CHMe)-Ho. 

Pyruvic Acid. Lactic Acid. 

470. Dibasic Acids. 1. Succinic Series. — Of this impor- 
tant series of acid*, which represents the second stage in the 
oxidation of the normal glycols, the following members are 
known : — 

Oxalic Acid Ho-(CO-CO)-Ho, 

Malonic Acid Ho-(CO-CH 2 CO)-Ho, 

Succinic Acid Ho-{CO-(CR 2 \-CO)-Ho, 

Pyrotartaric Acid JTo-(CO-( Cff 2 ) 3 - CO)- Ho, 

Adipic Acid Ho-(CO-(CH 2 ) f CO)-Ho, 

Pimelic Acid Ho-(CO-(CH 2 ),-CO)-Ho, 

Suberic Acid Ho-(CO-{CH 2 \-CO)-Ho, 

Anchoic Acid Ho-(CO-(CH 2 ) f COyHo, 

Sebacic Acid Ho-(CO~( CH 2 ) 8 -CO)-Ho, 

Roccellic Acid Ho -( CO'-( CH 2 ) U - CO)- Ho. 

With the exception of the first, each compound in the series 
admits of one or more modifications, the possible isomeric 
forms rapidly increasing with the number of carbon atoms in 
the olefine radical ; but the exact constitution of these bodies has 



470.] 



DIATOMIC COMPOUNDS. 



513 



been definitely fixed in only a few cases. The relation of the 
normal acids to the olefine radicals, which they are assumed to 
contain, is indicated by the following general synthetical method, 
by which they may be produced : — 

CN-{CH,) n -CN+ 2K-Ho + 2H 2 = 



Cyanide of .Radical. 



Ko-(CO-{CK,) n -CO) r Ko + 2NH,. [534] 



Potassic salt of Dibasic Acid 



When, on the other hand, these acids are acted on by agents, 
which determine the elimination of C0 2 from their molecules, 
they are converted first into monobasic acids of the acetic 
series, and then into hydrides of the olefine radicals. In some 
cases the action of heat alone is sufficient to produce the result, 
but in most cases the body must be heated with some caustic 
alkali or earth. It will readily be seen that by eliminating first 
one and then a second molecule of C0 2 from the diba>ic acid, 
the two compounds on the same line would be [successively 
formed. The name is omitted when it is not known that the 
product has been obtained by the reaction just indicated. 

Ho-(CO-CO)-Ho, 

Oxalic Acid. 

Ho-(CO-GH 2 -GG)-Ho, 

Alalonic Acid. 

ffo-(co-a 2 Ji f coyiro, 

Succinic Acid. 

Ho\CO-C,H, 2 CO)-Ho, 

Suberic Acid. 

M-(CO-C H H }ff COyiIo, 

Sebacic Acid. 

It will thus be seen how closely the acids of the succinic 
series are related to those of the acetic series, and the same 
point is still further illustrated by the following beautiful series 
of reactions by which acetic acid has been converted into 
malonic acid and the order of the changes described above 
reversed. 

Ho-(CO-CH s ) + Cl-Cl=Ho-(CO-CH 2 Cl) + HOI 

Ho-{CO-CH 2 Cl) +KCy = KCl+Ho-(CO-CIT 2 Ci/). [535] 

Ho\CO-CH 2 CN) + 2KHo=Ko\CO-CH 2 -CO)-Ko+NHz. 
22* GG 



Ho-(CO-H), 

Formic Acid. 


H-H, 

Hydrogen Gas. 


m-(co-cff 3 ), 

Acetic Acid. 


CH A , 

Marsh Gas. 


Ho-(CO-C 2 H 5 \ 

Propionic Acid. 


c 2 /4 


Ho-{CO-C,H n \ 


Hexylene Hydride. 


Ho-(CO-C 8 H 17 ), 


^8-" 18 
Octylene Hydride. 



514 ALCOHOLS AXD THEIR DERIVATIVES. [§471. 

In the same way succinic acid has been obtained from 
propionic acid, and formic acid may be changed into oxalic acid 
still more readily. 

2Ho-(CO-H) -f 2K-0-R= 

Ko-(CO-CO)-Ko + 2ff 2 + HH. 

471. Succinic Acid was originally prepared by distilling 
amber, and takes its name from the Latin name (succinium) 
of this fossil resin ; but it is now generally obtained by the fer- 
mentation of crude calcic maiate. It occurs ready formed in 
amber, in certain lignites, in some varieties of turpentine, and 
in several plants. This acid is a frequent product of the oxi- 
dation of organic substances, and is always formed together 
with other products when the fat acids are oxidized by nitric 
acid. Succinic acid itself singularly resists the action even of 
powerful oxidizing agents. It forms, like oxalic acid, three 
classes of .-alts, neutral acid, and super acid. When distilled 
it breaks up into water and an anhydride. 

Ho-(CO-C 2 H,-CO)-Ho= 0=((CO) 2 =CJI 4 ) +110. [536] 

Under the influence of nascent oxygen produced by electro- 
lysis it yields ethylene carbonic anhydride and water. 

B6-(CO-C 2 H i -COyffo+ 0= C 2 H i +2C0 2 -{- II 2 0. [537] 

472. Dibasic Acids. 2. Fumaric Series. — Two pets of 
isomeric compounds are known corresponding to two terms of 
a series of acids, which stand in the same relation to the suc- 
cinic series that the acrylic bears to the acetic. Thus we have 

Fumaric Maleic or Isomaleic Acids Ho-(CO-CJI 2 CO)-Ho, 
Itaconic Citraconic or Mesaconic Acids ffo-(CO-C 3 IIfCO)-Ho. 

The first term admits of only four modifications, and the 
choice of symbols for fumaric and maleic acids is limited by 
the fact that when acted on by nascent hydrogen they both 
give succinic acid. Furthermore, both acids combine directly 
with two atoms of bromine, and though the immediate products 
of this union are different, yet both bromo and isobromo-succinic 
acids, as they are called, produce the same succinic acid when 
the bromine is replaced by hydrogen. 



§473.] TRI ATOMIC COMPOUNDS.' 515 

The second term may be varied in no less than eleven dif- 
ferent ways, and the three formulae belonging to the three known 
acids cannot at present be recognized. 

These bodies, however, are related to pyrotartaric acid, just as 
the first set are to succinic acid. All three yield this product 
when acted on by nascent hydrogen, and all three combine 
with bromine, forming brominated acids which hydrogen con- 
verts into the same pyrotartaric acid as before. 

Fumaric and Maleic acids are both formed during the distil- 
lation of malic acid, from which they differ only by one mole- 
cule of water. 

Ho -( CO - CH f CHHo - CO)- Ho = 

MaiicAcid. Ho-{CO-C 2 H £ CO)-Ho-\-H 2 0. [538] 

Fumaric or Maleic Acid. 

Malic acid is the acid principle of apples, and of many other 
fruits. Fumaric acid is also found in certain plants, but 
maleic acid has not been met with ready formed in nature. 
Itaconic and citraconic acids are products of the distillation of 
citric acid. The third terms of both groups are products of 
special processes which cannot be traced. 



TRIATOMIC COMPOUNDS. 

473. Triatomic Alcohols, or Glycerines. — Common glycerine 
is the hydrate of the triad radical ( C 3 H d )= and has all the char- 
acteristics of a triatomic alcohol. The natural fats are mix- 
tures of various salts of the same radicals associated with acids 
of the acetic or oleic groups. When boiled with alkalies these 
salts are decomposed, a hydrate of the radical (glycerine) is 
formed, and alkaline salts of the fat acids result. The last are 
familiarly known as soaps, and such reactions are termed 
saponification. We can also saponify the fats with plumbic 
oxide, and then the lead soap (or " plaster ") being insoluble in 
water, while the glycerine is soluble, the products are easily 
separated. The fats may even be saponified by water alone, if 
acting at a high temperature, and glycerine is produced in the 
arts in large quantities by distilling the fats in a current of 
superheated steam. The products of the decomposition pass 
over together ; but, in consequence of their insolubility and low 
specific gravity, the fat acids separate from the glycerine in the 



516 ALCOHOLS AND THEIR DERIVATIVES. [§473. 

condenser. The reaction in one case is represented by the fol- 
lowing equation : — 

(C 9 H 6 yOf(C 1B ff 8li O) 9 + 3ff a O = 

s*™. (C 3 H 5 yOfH 3 + HfOf(O i8 H 35 0) 3 . [538] 

Glycerine. Stearic Acid. 

Glycerine, like all the true alcohols, readily exchanges B 2 of 
its radical for under the influence of oxidizing a gen s, and 
the acid product is called glyceric acid. Theory would lead 
us to expect two stages in this process, and two corresponding 
acids, thus : — » » 

(CB-CB 2 -CB 2 yO.^B s , 

GlyceriDC. — 4* 

( CB- CB 2 - COY- OfH*H, 

Glyceric Acid. — + 

(CO-CB-COyOfB,B 2 , 

Tartronie Acid. 

the first being triatomic and monobasic and the second triatomic 
and dibasic. The second acid has not as yet been produced 
by the direct oxidation of glycerine, but there can be little 
doubt that tartronie acid, which is formed by the spontaneous 
decomposition of nitro-tartaric acid, is the acid in question. 

When acted on by HI, glycerine is converted into isopropylic 
iodide. 

(CB 2 CB 2 -CByBo 3 + 5BI=z 

(CH 3 )f(CH)-I+3H a O + 2l-I. [539] 

The relations of glycerine to allylic alcohol and propylic 
glycol are illustrated by [491 et seq.~\ and [514]. 

Under the action of HGl glycerine exchanges Bo for CI in 
two successive stages, and by means of PCl 6 all three atoms of 
Bo may be thus replaced. 

(C 3 B 5 y-Ho 3y (C 3 Fr 5 y=Bo 2 ,ci, (c s B 5 yBo,a 2 , (C 3 H 6 yci 3 . 

Glycerine. Monochlorhydrine. Dichlorhydrine. Trichlorhydrine. • 

The compound (C 3 B 5 yBr s may be formed by a similar re- 
action, and by acting on this first with argentic acetate and then 
saponifying the "acetine" thus produced, glycerine may be re- 
generated. When acted on by a mixture of nitric and sul- 
phuric acid glycerine yields a highly explosive compound, nitro- 
glycerine, which may be regarded as a nitrate of glyceryl, or 
(C,B 5 yOi(N0 2 ) z (31). 



§474] TRIATOMIC COMPOUNDS. 517 

Theory would lead us to expect anhydrides of glycerine. 
The first anhydride (called Glycide) would have the symbol 
(0 3 H 5 yO,IIo, and although this body itself is not known, sev- 
eral of what may be regarded as its derivatives have been 
obtained. 

{C 3 H 5 yO,Ho, (C 8 H 5 )=-0,CI, (O s H 5 yOJ, (C,H 5 yHo,Cl,Br. 

By reactions similar to [521 et seq.~\, condensed glycerines 
have been formed. Thus we have 

{C z H f OCA)Wm, {CA-o-aH b -o-c,H,)iom, 

l>iglyceric Alcohol. Triglyceric Alcohol. 

which are evidently alcohols of higher atomicity than glycerine. 
Like similar polybasic compounds, they may be regarded as 
derived from a group of two or three molecules of glycerine 
by the elimination of a sufficient number of atoms of water to 
furnish the oxygen required to bind together the ba->ic radicals 
(151). Continuing this elimination still further we should 
obtain a series of anhydrides, one of which is known, viz. 
(O 3 H^0.rO 3 H 5 y0 2 -H 2 , and also a corresponding chlorhydrine 
(C,R 5 =0.fC\II 5 yJIo,L 

The following reactions illustrate the formation of some of 
the above compounds : — 

( C s H 5 y-Ho, Ol 2 + K-0 Hz= CzHf 0,01+ H 2 + KOI. 

( O z H 5 y 0, 01 + HBr = ( 3 ff 5 )-=Bo,Br, 01. [541] 

(O z H 5 yO,Ol+KI= (0 s ff 5 )=-O,I+ KOI. 

474. El hers of Glycerine. — By the action of Na~0-0 2 H b 
upon mono-, di-, and tri-chlorhydrine, we can replace either 
one, two, or all three of the atoms of typical hydrogen in gly- 
cerine with ethyl. The products have been called ethylines. 

(c 3 H & yo,H0 2 H & ),H 2 , (c&yo^c^jr, {c.h^o^cji^. 

Ethyline. Diethyline. Trieihyline. 

By heating glycerine with acetic acid the typical atoms of 
hydrogen may be replaced by the radical acetyl in the same 
three proportions : — 

(0,H,yOf{C 2 H,0)A 

Mono-acetine. ( ^^ Q ^ ^ ^ ^ 

DiaceUne. b ^ ^ Q% 

Triacetine. 



518 ALCOHOLS AND THEIR DERIVATIVES. [§475. 

Using in a similar way acids higher in the series, bodies similar 
to the fats may be produced. The natural oils and fats are 
mixtures of such salts, chiefly those of palmitic stearic and oleic 
acids. The solid fats consist chiefly of stearines and palmitines, 
and the liquid fats of oleines. The so-called drying oils, which 
when exposed to the air absorb oxygen and change to a dry resin- 
ous mass, are for the mo>t part" glyce rides " of acids not belong- 
ing to the acetic series, although closely related to it. All gly- 
cerides, when heated in the air, are decomposed and yield 
among other products acrolein whose penetrating odor is 
highly characteristic. This volatile body is formed abundantly 
when glycerine is heated with substances having a strong 
attraction for water, such as phosphoric anhydride, sulphuric 
acid, or still better acid potassic sulphate. 

( C 3 H 5 y- OiH, = 2B 2 0+( C 2 B 3 CO)- II. [542] 

Propylic alcohol, propylic glycol, and glycerine are all closely 
related compounds, and may be regarded as derived from the 
same hydrocarbon, 

C 3 B 7 -Bo = C 3 H 6 0, C 3 B ti =Bo 2 =C 3 B 6 2 , C 3 B^Bo 3 = C 3 II 8 3 , 

and hence common glycerine is distinguished as propyKc gly- 
cerine. Amylic glycerine, the only other compound of the 
series which has been produced, has not been thoroughly inves- 
tigated. 

475. Tnbasic Acid. — A triatomic acid of this class has 
been obtained from glycerine by the following reaction : — 

C 3 Hi-Br 3 + ZKCij = SKBr + C B HfCy z . 

[543] 
C 3 mCN) 3 + 3Kffo + 3II 2 0=C 3 IIf(CO-Ko) 3 +zriJ 3 . 

Glyceryl Cyanide. Potassic Tncarballylatc. 

The tricarballylic acid may be regarded as the third stage of 
oxidation from an unknown hexyl g'ycerine, and aconitic acid, 
found in the roots and leaves of monkshood, is the correspond- 
ing acryloid compound. 

Acetoid. Acryloid. 

Bo-CO-C 3 B 7y IIo-CO-CrA 

Butyric Acid. Crotonic Acid. 

( Ho - CO)t O s B 5 , (Ho - CO) : f C 3 II 3 . 

Tricarballylic Acid. Aconitic Acid. 



§476.] TETRATOMIC COMPOUNDS. 519 

Aconitic acid may be obtained by cautiously heating citric 
acid, but at the temperature of 160° it loses C0 2 and is con- 
verted into itaconic acid, already mentioned among the dia- 
tomic compounds. 

(Ho - 00) f C Z H Z — C0 2 ={Ho- GO) 2 = C 3 R 4 . [544] 

Aconitic Acid. Itaconic Acid. 

Citric acid, the well-known acid principle of the lemon, but 
which is also found in many other fruits, although only tribasic, 
is tetratomic and therefore belongs to the next division. It 
differs from aconilic acid by only a single molecule of water, 

{Ho-CO)fC^-Ho — H 2 = {Ho-CO)fCzH Bi [545] 

Citric Acid. Aconitic Acid. 

and hence the transformations which it undergoes when 
heated (472). 

TETRATOMIC COMPOUNDS. 

476. Tetratomic Alcohol. — Erythrite, a white crystalline 
material extracted from various lichens, is regarded as an alco- 
hol of this class. It combines with the fat acids, forming 
ethers, and it contains, as the symbol given below indicates, 

i four atoms of typical hydrogen. The following reaction ex- 
hibits its constitution, and the symbols which follow show its 
relations to butylic alcohol. 



C 4 H b ^Ho 4 + 1HI = a,H s =KI -f 4i7 2 + 3I-I. [546] 

Erythrite. Butylene Iodo-hydride. 

C A H W C 4 ff w O, C 4 ff„0 2 , C A H in O,. C 4 H,«0 4 . 

utylic Hydride. Butylic Alcohol. Butylic Glycol. Unknown Glycerine. Erythrite. 



Theory would lead us to expect three acids from the oxida- 
tion of erythrite, but of these only one is known. The second 
derivative is tartaric acid, whose tetratomic and dibasic char- 
acter, already illustrated (209), is thus explained : — 

CJI=0=% CJJ,0=0=H^H, CJip=0=H 2i H 2 , C/)*0 ^H,H.j 

Erythrite. Unknown. Tartaric Acid. Unknown. 

- + 

Citric acid, C & H 4 0^0 4 =H,Hz, is a homologue of the unknown 
third derivative, and may be regarded as derived in the same 
way from an unknown alcohol of this series. 



520 ALCOHOLS AND THEIR DERIVATIVES. [§477. 

Tartaric acid is closely allied both to malic and succinic acids. 
Malic acid is a homologue of tartaronic acid, and both have al- 
ready been mentioned. As the following symbols show, they 
differ, each from the next in order, by a single atom of oxygen. 

C 4 ff 6 0„ C<H 6 5 , C 4 II,0 6 , 

or + or _ + or _ ■ + 

C 4 ff 4 O.f 0.fff 2 , CJJ Z Of OfH,H 2 , C 4 ff 2 Of 0£H 2 ,H 2 . 

Succinic Acid. Malic Acid. Tartaric Acid. 

When tartaric acid is heated with HI it is reduced first to 
malic acid, and then to succinic acid, and on the other hand by 
treating brorno- and dibromo- succinic acids with water and 
argentic oxide the reverse change may be effected. The re- 
markable isomeric moditications of tartaric acids have already 
been noticed (70), (85). 

HEXATOMIC COMPOUNDS. 

477. Mannite. — No well-defined pentatomic compounds are 
known, but several hexatomic compounds have been distin- 
guished, and it is probable that many of saccharine bodies be- 
long to this class. By extracting common manna (the ex- 
udation from several species of ash) with boiling alcohol we 
easily obtain a highly crystalline white solid, slightly sweet to 
the taste, which is called mannite. This substance is a hexa- 
tomic alcohol, and its composition is represented by the symbol 
CqH^IOqIHq. Its constitution is indicated by the following cir- 
cumstances : 1. When treated with a mixture of nitric and 
sulphuric acids it yields a product similar to nitro-glycerine 
C 6 H^O^{N0 2 ) & . 2. It forms numerous compounds with the 
fat acids, in which, as before, six atoms of hydrogen are re- 
placed by the acid radical ; for example, the symbol of the 
compound with stearic acid is (7 6 /^l(9<.i( C, 8 /£ 5 0) 6 . 3. It is 
acted on by HI'm a similar manner to erythrite aud glycerine. 

C 6 B s mo 6 -f UHI= Qff^HI 1 + 0>H 2 O -f hl-L [547] 

4. By means of oxidizing agents mannite may he converted into 
two acids, — mannitic acid, Hq=0 6 = C g II 6 0, and saccharic acid, 
Hq\0 & ICqH 4 2 , — which bear the same relation to this hexatomic 
alcohol that glyceric and tartaronic acids bear to glycerine. 

1 The products obtained in [539], [546], and [547], although isomeric with 



§478.] HEXATOMIC COMPOUNDS. 521 

478. Saccharine and Amylaceous Bodies. — Woody fibre, or 
cellulose, starch, gum, and sugar, together with water, consti- 
tute the great mass of all vegetable organism, and are the 
materials on which the animal chiefly subsists. But although 
these bodies play such an important part both in vegetable and 
animal physiology, we have but little knowledge of their 
chemical constitution beyond their empirical formulas. They 
have been divided into three classes, — 1st. The Amyloses, in- 
cluding woody fibre, starch, and gum, all of which are materials 
incapable of crystallization, and for the most part organized. 
2d. Sucroses, including cane sugar, sugar of milk, and the 
sugars from different varieties of manna, which have a crys- 
talline structure, but are not susceptible of direct fermenta- 
tion. 3d. Glucoses, including grape sugar and fruit sugar, 
which, under the influence of yeast, break up into alcohol and 
carbonic anhydride. 

These bodies contain hydrogen and oxygen in the propor- 
tions to form water, and therefore have been called the hy- 
drates of carbon ; but there is no reason for believing that the 
atoms are grouped as this name would indicate. The com- 
position of the bodies of each class is essentially the same, 
and may be represented by the following symbols : — 

Amyloses, (7^0 (9 5 ; Sucroses, G n H n lx \ Glucoses, C^R 12 6 . 

It is probable, however, that some of them ought to be repre- 
sented by multiples of these formulas, and several of them 
contain in addition one or more molecules of water of crys- 
tallization. 

The glucoses have evidently the simplest molecular structure 
of this class of bodies. They consist for the most part of two 
isomeric substances which are most readily distingu^hed by the 
action which they exert when in solution on the plane of polar- 
ization of a ray of light. One turns the plane to the right and 
the other to the left (85), and hence they have been called 

the iodides of the alcohol radicals, are not identical with them. If treated 
with Ag*0 and H«_0. they are converted into pseudo-alcohols similar to iso- 
propylic alcohol, and their symbols may be written on either of the two types 
represented in the reactions just referred to. Thus we may write 

arr^nr. or {arhUQff^Hrffhi. 

Hexylewe lodo-hydride. Iso-hexylic Iodide. 



522 ALCOHOLS AND THEIR DERIVATIVES. [§479. 

Dextrose and Levulose. They are found mixed together in 
honey, in the juices of acid fruits, and in the uncrystallizable 
sirups, called molasses, formed in the extraction of sugar, and 
they may readily be produced artificially by the action of dilute 
acids and certain ferments on the different varieties of starch 
and sugar. When common starch is heated with dilute sul- 
phuric acid, it changes into dextrose ; but a variety of starch ex- 
tracted from the dahlia-root changes under the same conditions 
into levulose. Cane-sugar under similar influence forms a 
mixture of dextrose and levulose. 

C 12 H 22 O a -f H 2 = a 6 R l2 d e + C 6 ff l2 6 . [548] 

Sucrose. Dextrose. Levulose. 

The acid acts merely by its presence, and remains unchanged 
during the process. Nitric acid oxidizes glucose to saccharic 
or oxalic acids ; and under the influence of nascent hydrogen 
levulose changes to mannite. We may, therefore, regard it as 
the aldehyde of this hexatomic alcohol. 

G ff u O Q , Cq^oOq, C g 1T }2 7 , CcHxqOz. 

Mannite. Levulose. Mannitic Acid. Saccharic Acid. 

By the action of nitric acid on milk, sugar, or gum-arabic, 
an acid isomeric with saccharic acid called mucicacid is formed, 
and by the gentle action of nitric acid on saccharic acid tartaric 
acid may be produced. 

All the amylaceous and saccharine bodies form more or less 
stable compounds with strong bases, and most of them when 
treated with a mixture of nitric and sulphuric acids yield pro- 
ducts similar to nitro-glycerine, of which gun-cotton (31) is the 
best known. 

479. Glucosides. — Under the prolonged influence of heat, 
glucose has been united with acetic, butyric, stearic, and 
benzoic ac'ds, and a class of compounds obtained similar to the 
fats. The compound formed with acetic acid is represented by 
the symbol ( CJ;^T 4 5 )i( C 2 ff 3 0) 6 . These glucosides are interest- 
ing because they are probably allied to a class of substances 
found in many plants, which under the influence of ferments 
yield glucose, together with other bodies. The most important 
are : — 

1. Amygdaline, found in bitter almonds, together with an 



§480.] HEXATOMIC COMPOUNDS. 523 

albuminous substance called synaptase, which when the almond 
meats are bruised determines the following reaction : — 

C 2 ,H 27 N0 X1 + 2H 2 = C 7 H, -f- HON -f 2 C & ff 12 6 . [549] 

Amygdaline. Oil of Bitter Glucose. 

Almonds. 

2. Salicine, contained in the pith of the willow and poplar, 
which in presence of certain ferments is decomposed as 
follows : — 

OvtHis 7 + H 2 = C 7 R 8 2 + C c> ff u 6 . [550] 

Salicine. Saligenine. Glucose. 

3. Tannine or Tannic Acid, widely diffused in the bark of 
plants, and well known for forming an insoluble compound 
with gelatine (as in tanning leather), and for producing a black 
color (ink) with ferric salts. This body when exposed in a 
moist state to the air, or treated with dilute acid, forms glucose 
and gallic acid. 

C 27 ff 22 O i7 + ±H 2 = SC 7 R,0 5 + C,ff ]2 G . [551] 

Tannine. Gallic Acid. Glucose. 

480. Fermentation. — This term is applied to a number of 
remarkable chemical processes, which depend upon the life and 
growth of a very low order of organized beings, belonging 
chiefly to the vegetable kingdom. These organisms are the 
efficient part of what is called the ferment or yeast. The fer- 
menting material is their appropriate food, and the products of 
fermentation are in some unknown way determined by the 
vital process, different ferments, that is different organisms, 
producing different results. Moreover, we can frequently dis- 
tinguish between the growth and propagation of these organisms, 
and the normal vital proces-, by which the products of fermen- 
tation are evolved; the first requiring the presence of certain 
materials, chiefly albuminous, which otherwise take no part in 
the chemical change. The germs of these living beings are 
widely diffused, floating even in the atmosphere, and begin at 
once to grow as soon as a fermentable liquid and the right 
temperature supply the conditions of active life. Fermentation, 
therefore, may set in without the apparent addition of any fer- 
ment, and on the other hand the change may be prevented by 
sealing up the material in air-tight cans previou-ly heated to 
such a temperature as will insure the destruction of all living 
germs. 



524 ALCOHOLS AND THEIR DERIVATIVES. [§481. 

The principal modes of fermentation are : — 

1. Alcoholic fermentation caused by a fungus, the Torvula 
cerevisias, commonly called yeast, which converts glucose into 
alcohol and carbonic anhydride, forming, however, at the same 
time a small amount of succinic acid and glycerine. 

C,H l2 6 = 2 C 2 H Q + 2 C0 2 . [552] 

2. Acetous fermentation, induced by the Mycoderma vini, by 
which alcohol is changed into vinegar. 

3. Lactic fermentation, in which the Penieillium glaucum 
converts saccharine materials into lactic acid. 

C«H V2 6 =2 C,If, 3 . [553] 

Glucose. Lactic Acid. 

4. Butyric fermentation, supposed to be caused by an animal, 
in which lactic acid, formed as above, is changed into butyric 
acid. 

2 C,H, 3 = C 4 H S 2 + 2 C0 2 + 2IIK [554] 

5. Mucous fermentation, which sugar undergoes under the 
influence of the *' mucous ferment," giving rise to the escape 
of carbonic anhydride and hydrogen, and the formation of 
mannite, together with a peculiar gum and a mucilaginous 
substance. 

481. Conclusion. — The different forms of fermentation are 
but lower modes of the manifestation of that obscure power by 
which animals and plants not only prepare the materials of their 
tissues, but also secrete from their organisms the various pro- 
ducts of their vital processes. As has been shown, we have 
been able, to a limited extent, to achieve in our laboratories the 
same results, and we can see no limit to our synthetical meth- 
ods. Nevertheless, we have not been able as yet to produce 
any of the materials which make up the great mass of the tis- 
sues of all organized beings, and this, which is true of the gum, 
starch, and woody fibre of plants, is true to a still greater de- 
gree of such materials as albumen, caseine. gelatine, fibrine, &c, 
which are the main constituents of the animal body. In regard 
to the composition of these nitrogenized compounds we have no 
knowledge except that which may be obtained by ultimate 



§481.] HEXATOMIC COMPOUNDS. 525 

analysis ; and although we have every reason to believe that 
future investigation will reveal their molecular constitution, so 
far as they are simple chemical compounds, yet in most cases 
the substance of these bodies cannot be isolated from the organic 
structure which determines in a great measure their distinctive 
qualities ; and not only has man never been able to make the 
simplest organic cell, but the whole process of its growth and 
development is utterly beyond the range of his conceptions. 
Moreover, even in regard to those simpler products of organic 
life which we have been able to reach by synthesis, we have no 
knowledge of the processes by which they are formed in organic 
nature. 

The vegetable kingdom is a great laboratory, in which the 
sun's rays manufacture from the gases of the atmosphere, and 
from a few earthy salts of the soil, the different materials which 
the organic builders employ. The animal, unlike the plant, has 
not the power of forming the substance of its tissues from inor- 
ganic compounds, but it receives from the vegetable laboratory 
the materials required ready formed. It transmutes these pro- 
ducts into a thousand shapes in order to adapt them to its wants ; 
but its peculiar province is to assimilate and consume, not to 
produce. The nitrogenized compounds just referred to are the 
portion of its food which supplies the constant waste attending 
all the vital processes. The non-nitrogenized starch and sugar, 
although they form the greater part of our food, are never incor- 
porated into the tissues of the body, but are merely the fuel by 
which its temperature is maintained. Here, however, chem- 
istry stops, and the science of physiology begins. 

In closing this summary of facts, we must remind the student 
that, as we stated in the introduction, we have made no attempt 
at completeness. Although the chief characteristics of all the 
chemical elements have been illustrated, yet important classes 
of compounds have been necessarily left unnoticed, and this is 
especially true in the last division of the book. Organic chem- 
istry presents such a vast array of facts that the attempt to 
comprehend the whole field would simply lead to confusion, and 
serve no useful end. "We have, therefore, limited our scope to 
those classes of compounds whose molecular structure is well 
understood, and our great object has been to illustrate the 
methods by which a knowledge of this structure has been 



526 QUESTIONS AND PROBLEMS. [§481. 

reached. It is by these methods that the new philosophy of 
chemistry is chiefly distinguished from the old, and to them we 
shall especially direct the student's attention in the questions 
which follow. He should not content himself, however, with 
simply answering these questions, but, by an exhaustive study 
of all the reactions which have been given, and by a constant 
use of graphic symbols, endeavor to become imbued with the 
spirit of the philosophy which it has been the object of this 
book to illustrate. 



Questions and Problems. 
Carbon and Oxygen. 

1. Deduce the atomic weight of carbon, and state the facts and 
principles on which the conclusion is based. 

2. When the product of the combustion of coal is CO, what pro- 
portion of the calorific power of the fuel is lost ? (61). 

3. Is the combination of C0 2 with additional carbon in passing 
through a mass of incandescent coal attended with an evolution or 
an absorption of heat ? Estimate the amount of the effect pro- 
duced. 

4. Illustrate by examples and seek to establish by reactions or 
other facts the oxatyl theory of the constitution of organic acids. 

Carbon and Nitrogen. 

5. On what facts is the symbol of cyanogen gas based ? 

6. In what respects does HCy resemble, and how does it differ, 
from the hydrogen acids of the chlorine group ? 

7. What is the distinction between the two classes of double 
metallic cyanides ? 

8. Represent by graphic symbols the constitution of several of the 
polymeric compounds of cyanogen, including the ferro and ferri- 
cyanides of potassium. 

9. What proof is furnished by the reactions of (425) that the 
amine and amide compounds, there mentioned, have the constitution 
represented by the symbols assigned to them ? 

10. Repeat the reactions given in (425), writing the symbol of 
cyanic ether after the ammonia type. 

11. Represent by graphic symbols the constitution of cyanic 



QUESTIONS AND PROBLEMS. 527 

ether and cyanetholine respectively, and give the reactions from 
•which the symbols are' deduced. 

12. Urea, when in solution in water, changes into amnionic car- 
bonate. Write the reaction. 

Carbon and Hydrogen. 

13. How many essentially different modes of grouping are possi- 
ble with a carbon skeleton of four atoms, assuming that no atom is 
united to any one of its neighbors by more than one of its affinities? 
How many with a skeleton of five atoms, &c. ? 

14. Make a table of the possible hydrocarbons in series of homo- 
logues and isologues. 

15. How many essentially different modes of grouping are possi- 
ble with the compounds C 6 H W CJ1 W and C 6 Z7 6 ? 

16. Is the number of H atoms in the molecule of a hydrocarbon 
necessarily an even number ? 

17. Is any evidence given of the synthesis of marsh gas ? 

18. Why may the three expressions C 2 /7 5 C 2 H & , C ;i H 7 CH s and 
CJI l0 represent identical compounds ? 

19. Explain the manner in which the successive hydrogen atoms 
of C i H i may be replaced by bromine. 

20. Write the symbols of the different hydrocarbons of the 
phenyl series on the assumption that they all contain the radical 
C 6 H ro united to the radicals of the methyl series, and show how many 
isomeric modifications are possible in each ca?e. 

21. Describe the method of preparing aniline from benzol. 

22. Show by graphic symbols the relations of the radicals allyl 
and glyceryl. 

23. Illustrate by graphic symbols the relations of the oxygenated 
to the simple hydrocarbon radicals, and explain the principle stated 
in (436). 

Monatomic Alcohols, &fc. Marsh Gas Series. 

24. Represent graphically the constitution of the alcohols of the 
marsh gas series, and show that the reactions of (438) sustain your 
theory. 

25. Write a series of reactions by which the synthesis of propylic 
alcohol can be effected, starting with mineral substances. 

26. Analyze reactions [438] and [439], and trace the action of 
nascent hydrogen and N 2 O z in these cases as illustrating their use 
as reagents in organic chemistry. 



528 QUESTIONS AND PROBLEMS. 

27. What general method of preparing the amines (167) is indi- 
cated by [438] ? 

28. Show that the constitution of acetic acid may be deduced 
from [374], [443], [448], and [449]. 

29. Write a series of reactions by -which acetic acid may be 
converted into propionic acid. 

30. What is the use of P„0 6 as a reagent in organic chemistry 
[445] ? 

31. Analyze reaction [444] and show what an important effect 
can be produced by the action of potassic hydrate on the cyanide 
of a hydrocarbon radical. Compare [389]. 

32. What conclusions would you deduce from reactions [450] to 
[452] in regard to the constitution of the fat acids ? Llu&trate by 
developing in full the rational formula of butyric acid. 

33. What are the several sources of palmitic acid ? 

34. Compare the constitution of iso-butyric and iso valeric acids 
obtained by [456] and [457] with the normal compounds. Are 
other isomers possible ? 

35. Write the reactions by which methylic ether is prepared. 

36. Explain the process of etherification as illustrated by [458] 
and [459]. What is the essential difference of conditions in the 
two reactions ? 

37. Write the reactions by which common ether may be obtained 
after [461]. 

38. Make a table of the different ethers. 

39. All the hydrogen atoms of methylic ether may be replaced 
by chlorine in successive pairs. Write the symbols of the compounds 
thus formed. 

40. Analyze reactions [461] as illustrating the use of sodium as a 
reagent in organic chemistry. 

41. Describe the methods of preparing the compound ethers, and 
compare them with the reactions by which mineral salts are ob- 
tained. 

42. Show in what way the presence of a strong acid assists the 
reactions expressed by [466] and [467]. 

43. To what does saponification correspond in mineral chemistry ? 

44. Write the reaction of water on acetic ether. 

45. Write the reaction by which butyric anhydride may be pre- 
pared. 



QUESTIONS AND PROBLEMS. 529 

46. Write the reaction of water on acetic anhydride. 

47. Compare the effects of PCl 3 and PCl 5 when used as reagents 
in organic chemistry, so far as illustrated by [471] and [34]. 

48. In what manner may the haloid ethers be converted into 
amines ? 

49. Chloroform may be regarded as the chloride of the trivalent 
radical C1I. Do you know of any reaction which illustrates this 
point ? 

50. Analyze the reactions by which the aldehydes are formed, 
and show how far they indicate the constitution of these bodies. 

51. Write the reaction which takes place when the aldehydes are 
heated with potassic hydrate. 

52. Represent by graphic symbols the constitution of the alde- 
hydes and ketones, and show that the chemical relations of the two 
classes ot isomeric compounds are the result of a diffeienee of atomic 
grouping. Show also that your theory of the constitution of these 
bodies is a legitimate inference from the reactions, of which they 
are susceptible. 

53. Illustrate by graphic symbols the difference between the 
pseudo-alcohols and the normal compounds and the relations in which 
they stand to the ketones and aldehydes respectively. Show that 
the symbols assigned to the normal and secondary alcohols are le- 
gitimately deduced. 

54. Compare by the graphic method the constitution of the three 
classes of alcohols. Take heptyl alcohol with its isomers as an ex- 
ample, and point nut the differences in the carbon skeletons of these 
isomeric compound*. In what does a normal alcohol consist ? 

55. M*ke a Uhle exhibiting the relations of the different com- 
pounds of the marsh gas series including hydrocarbons, alcohols, 
acids, aldehydes, acetones, and ethers. 

Vinyl Series. 

56. The differences between the vinylic and ethylic alcohols may 
be referred to what differences in the structure of the carbon skele- 
ton of these two classes of compounds ? What proof have you 
that such a difference exists ? 

57. Compare by the graphic method the difference between 
vinylic alcohol, acetic aldehyde, and ethylenic oxide, and give the 
reasons for your mode of grouping the atoms. 

58. Why should you not expect to obtain an acid from vinylic 

25 HH 



530 QUESTIONS AND PROBLEMS. 

alcohol by the action of oxidizing agents, when allylic alcohol yields 
both an aldehyde and an acid ? 

59. Write the reaction by which allylic alcohol is converted into 
acrolein and acrylic acid. 

60. How far is the change from glycerine into acrolein attended 
with a change of type V 

61. In what does the difference between the structure of the 
acids of the acrylic and acetic series consist ? 

62. Carefully analyze the reactions by which different types of 
structure in the acrylic series have been obtained, and show th^t the 
conclusions reached are legitimate. 

63. How and under what conditions does PCl 3 act as a dehy- 
drating agent ? 

64. In what way does [444] and [505] indicate the structure of 
/3 crotomc acid ? 

65. Give the general symbols of the three classes of acryloid 
acids. 

Phenyl Series. 

66. Represent the constitution of benzoic alcohol by graphic 
symbols, and show how far its structure resembles that of the alco- 
hol of the ethjlic series containing the same number of carbon 
atoms. Compare the carbon skeletons of the two compounds. 

67. Why is it that carbolic acid, although homologous with benzoic 
alcohol, differs from it so greatly in its chemical relations ? 

68. How is toluol related to benzol, and by what series of reac- 
tions miy the first be changed into the last ? 

69. How is cressylic alcohol related to carbolic acid ? Represent 
with graphic symbols the structure of the two bodies. 

70. Write the taction by which benzoic acid is produced from 
hippuric acid (168). 

71. Represent graphically the relations of cinnamic to benzoic 
acid, and point out the difference of structure in the carbon skele- 
ton of the two compounds. What similar relations have previously 
been noticed ? 

72. Represent graphically the relations of salicylic acid to ben- 
zoic acids. What acid stands in a similar relation to acetic acid ? 

73. Make a table exhibiting the relations of the different com- 
pounds of the radical phenyl, with their possible homologues, and 
show how far the reactions, which have been given, indicate their 
molecular structure. 



QUESTIONS AND PROBLEMS. 531 

Diatomic Alcohols, Sfc. 

74. Describe the several processes by which the glycols may be 
produced. 

75. Illustrate by graphic symbols the constitution and relations of 
the different derivatives uf ethylie glycol, especially of the ehlorhy- 
drines, bromhydrines, &c. 

76. Point out the differences between the chemical relations of 
ethylie oxide (common ether) and ethylenic oxide, and show how far 
they may be explained by differences of structure. 

77. Describe the reactions, by which condensed glycols maybe 
produced, and cite examples of similar compounds from the mineral 
kingdom. What proof is there that these compounds have- the 
strurture assigned to them, and why can greater certainty be reached 
in regard to the structure of these bodies than in regard to that of 
the mineral products they are said to explain ? 

78. Illustrate by graphic symbols the structure of the three chief 
classes of acids of the lactic family, and show in each case how the 
conclusion has been reached. 

79. Construct the graphic symbols of ethylene and ethylidene, 
and give the reasons for the forms adopted. 

80. Show that the constitution of the known glycols can be 
inferred from that of the acids of the lactic family. 

81. What is meant by an olefine acid ? In what way must the 
carbon atoms in the defines be arranged ? Show that the conclu- 
sion is trustworthy. 

82. Compare the reaction of potassic hydrate on cyanhydrine of 
eth)lene and on cyanhydrine of ethylidene. Can you draw any 
legitimate inference in these cases as to the structure of the result- 
ing compounds ? 

83. Explain the term etheric acids. Has any example of such 
compounds been previously given ? 

84. Represent by graphic symbols the constitution of the isomeric 
compounds cited in (467), and inquire whether further variations 
are possible. 

85. Write the reactions, 1. of lactic acid on sodic carbonate, 2. 
of sodium on sodic lactate, 3. of ethylie iodide on disodic lactate. 

86. What is the general action of HI as a reagent in organic 

chemistry ? [530.] 

87. "Write the reaction of potassic hydrate on cyanide of ethylene, 
and show how far this establishes the constitution of succinic acid. 



532 QUESTIONS A2CD MOSLEMS, 

88. Write the reaction which takes place when one molecule of 
C0 2 is eliminated from milunic acid by the action of heat, or when 
succinic acid is decomposed in a similar way if heattd with lime. 

89. Write the reaction when suberic acid is heated with exeesg 
of baryta. 

90. What is the general action of lime or baryta when heated 
with an organic acid ? 

91. Show by graphic symbols how the acids of the succinic series 
are related to those of the acetic series, and describe the methods 
by which one e^s of compounds may be converted into the other. 

92. Show that reactions [536] and [537] confirm the conclusion 
already reached in regard to the constitution of succ'nie acid. 

93. In what isomeric form may the symbol of succinic acid be 
written, and what radical would it then contain, in place of ethy- 
lene ? What proof have you that it does contain ethylene ? 

94. Succinic acid is formed when butyric acid is oxidized (by 
nitric acid). Write the reaction. 

95. Write the general symbols of the three classes of the succi- 
nates both of univalent and bivalent radicals. 

96. What is the characteristic of an acrjloid acid? Show that 
fumaric acid conforms to this type. 

97. Show by graphic symbols the possible forms of the first term 
of the fumaric series. 

98. Show how far the fact that both fumaric and mal ic acids 
yield succinic acid, under the influence of nascent h)drogen, fixes 
their symbols. Show also that the brominated compounds may be 
different; while the further products obtained by the action of 
nascent hydrogen on the last may be identical. 

99. Represent graphically some of the possible forms of the 
second term of the fumaric series, and trace the relations of these 
compounds to pyrotartaric acid. 

100. Compare the graphic symbols of succinic, fumaric, and malic 
acids. 

Triatomic Compounds. 

101. Write the reaction on stearine, 1. of solution of potassic 
hydrate, 2. of plumbic oxide and water, 3. of superheated steam. 

102. Compare the graphic symbols of glycerine, glyceric acid, 
and tartaronic acid, and explain their atomic and basic relations. 



QUESTIONS AND PROBLEMS. 533 

103. How far do the reactions [514] and [539] indicate the 
construction of the basic radical of glycerine ? 

104. Write the reaction by which the several chlorhydrines of 
glycerine are obtained, and point out their relations to the triatomic 
character of the compound. 

105. Compare the anhydrides of glycerine with the polybasic 
mineral compounds. 

106. Give the symbols of the three stearines and the three oleines 
corresponding to the three acetines. 

107. Exhibit by graphic symbols the relations of glycerine to 
acrolein. 

108. Compare graphically the relations of prop) lie alcohol, pro- 
pylic glycol, and glycerine. 

109. A normal alcohol may be converted into an acid either by 
oxidation or by a reaction similar to [543] ; compare the results 
obtained, and show the bearing of the facts on the oxatyl theory of 
organic acids. 

110. AVrite the symbols of the different acids which might theo- 
retically be formed by the oxidation of the assumed hexyl glycerine. 

Ill Compare the graphic symbols of tricarballylic and aconitic 
acids. 

112. Compare the graphic symbols of citric, aconitic, and itaconic 
acids, and explain the change of the first into the last through the 
second. 

Tetratomic Alcohols, fyc. 

113. Make a table exhibiting the relations of tartaric and citric 
acids to the tetratomic alcohols. 

114. When tartaric acid is reduced by HI, it changes first into 
malic and then into succinic acid. Write the reactions and inquire 
how far they aid in establishing the constitution of the bodies in- 
volved. 

115. Compare the carbon skeletons of one or more of each of 
the classes of acids which have been studied, and show that the 
variations are limited to a few principal types. Then, by attaching 
atoms of H, Ho, NH 2 , COHo or O to these skeletons, illustrate the 
relations of ihe various classes of compounds which may be formed 
around a common nucleus. 



CHAPTER XX. 



APPENDIX. 



Complex Amines, 

482. Aniline Colors. — These beautiful products of modern 
chemistry, which are so highly valued on account of their bril- 
liant hues and wonderful tinctorial power, belong to the class 
of compounds called amines, whose chemical relations have 
been already described (167). They are, so far as known, 
highly complex bodies of the ammonia type, and will serve to ex- 
tend our knowledge of this class of compounds, connecting them 
with the compounds of the hydro-carbon radicals, with which 
we have become more recently acquainted. The processes by 
which the aniline dyes are prepared in the arts consist chiefly 
in the oxidation of a mixture of aniline and toluidine, but the 
precise reactions involved can seldom be traced. Nevertheless 
we have been able to reach a general knowledge of their con- 
stitution, although it must be held subject to revision by the 
results of the ever-widening investigations, which the great 
interest of these beautiful bodies invites. 

The process by which aniline is obtained from benzol has 
been already described, and toluidine is prepared in precisely 
the same way from toluol (434). By the action of oxidizing 
agents on these monamines we can obtain four distinct triamine 
bases, whose salts are all deeply colored. Each molecule of the 
raonamine loses by oxidation two atoms of hydrogen, and then 
three of these dehydrated molecules coalesce to form one mole- 
cule of the complex triamine, thus : — 

SCeHir&ffi —6H= C 18 FT/ l N,=ff 3 . 

Aniline. Violaniline. 

2C (i H f N'=H 2 + C 7 B 7 -N-H 2 — 6#= C ld H^N^H z . 

Aniline. Toluidine. Mauvaniline. 

C 6 H b -N=H 2 + 2C 7 H 7 -N-K 2 — QII= C^ff^NfH^. 

Aniline. Toluidine. Rosaniline 

2>C 7 H 7 -N-H 2 — 6H=: C^H^NtH^ 

Toluidine. Chryaotoluidine. 



§482.] ANILINE COLORS. 535 

The simplest conception we can form of the constitution of 
these products is indicated below : — 

C 6 H, C 7 H^ 

NH NH NH NH 

QHfNHC,H 4 C«H f NH-C 6 H 4 

Yiolaniline. Mauvaniline. 

CjJJq G?^6 

NH NH NH NH 

C 7 H G -NH C& C 7 H 6 -NH- 6 T H 6 

Rosaniline. Chrysotoluidine. 

and it can easily be seen that such a grouping might readily 
result, if we assume that of the two atoms of hydrogen which 
each molecule of the monamine loses, one is torn from the ni- 
trogen atom and the other from the benzol nucleus. All we 
know, however, with any certainty, is that there remain three 
atdtns of typical hydrogen, which may be further replaced by 
various hydro-carbon radicals, and this is expressed by the first 
set of symbols. 

Of these bases rosaniline is practically the mo-t important. 
The usual process by which its compounds are manufactured 
in the arts consists of three stages: first, the conversion of 
benzol and toluol (obtained from coal-tar naphtha by fractional 
distillation) into nitio-benzol and nitro-toluol (434) ; second, the 
reduction of these nitro-compounds (usually by mixing them 
with acetic acid and iron-turning-) to aniline and toluidine 
[428] ; third, the oxidation of a mixture of these bases, in 
about the proportions of one of aniline to two of toluidine, by 
means of arsenic acid. To this end the mixture is treated with 
a concentrated sirupy solution of the reagent, and the whole 
mass is heated to about 150°, and kept at this temperature un- 
der constant stirring for several hours. The crude product, 
a resinous solid with a bronze-like lustre, is dissolved in boiling 
water, and a large excess of sodic chloride added, which precipi- 
tates chloride of rosaniline in crystals, that reflect beautiful chang- 
ing green hues like beetles' wings, but are red by transmitted 
light, and yield with alcohol or acetic acid deep red solutions. 
From the chloride the other salts of the same base may be readily 
prepared, including the hydrate, C^H^N^ . 2H 2 0, which falls as a 



536 ANILINE COLORS. [§482. 

brownish-yellow precipitate on adding caustic soda or ammonia 
to a solution of any of the aniline reds of commerce, but when 
purified it is colorless, becoming, however, rose-red on exposure 
to any acid, even the carbonic acid of the atmosphere. It is 
a singular fact in regard to all the bases mentioned above, that, 
while all their salts are such powerful pigments, they are them- 
selves colorless. The hydrate of rosaniline is insoluble in ether 
or coal-tar, nearly so in water, only slightly soluble in aqua 
ammonia, but dissolves with readiness in alcohol, with which it 
forms deep red solutions. With acids it forms three classes of 
salts, neutral, acid, and di-acid, which crystallize readily. It is 
the last of these which are so remarkable for their beetle-like 
lustre and give such beautiful rose-red solutions, and they are 
the true coloring compounds. A great variety of these, in- 
cluding besides the arseniate the chloride, nitrate, sulphate, chro- 
mate, acetate, oxalate, and tannate, are used in the arts and 
known under fanciful names, such as magenta, azaliene, fuch- 
sine, roseine, &c. They are most of them freely soluble. in 
water and alcohol, but the tannate is so insoluble that it is used 
for fixing the color upon calico and recovering the dye from 
nearly spent solutions. 

It was discovered by Hofmann that the three atoms of typical 
hydrogen remaining in rosaniline may be replaced by the hy- 
dro-carbon radicals, and these replacements give rise to beau- 
tiful violet and blue pigments. The so-called Hofmann's violets 
and blues are salts of mono, di, or tri phenylic, ethylic, or me- 
thylic rosaniline ; and the further the substitution is carried, the 
more do the blue tints preponderate in the resulting dye. The 
phenylic compounds are obtained by heating the salts of rosani- 
line wilh aniline under pressure, and the ethylic or methylic 
compounds may be prepared by treating the rosaniline salts 
with the iodides or bromides of ethyl or methyl. 

Besides the definite compounds, whose chemical relations 
have been described above, there are prepared in the arts a 
very great variety of other aniline dyes, including greens, yel- 
lows, blacks, and indeed almost every color. They are all 
probably compounds of one of the four bases described above, 
or of analogous bases derived from them, but they are fre- 
quently mixtures, and from the empirical processes by which 
they are prepared we can draw no definite conclusion as to 
their precise constitution. 



§ 483.] UREA. 537 



Complex Amides. 

483. Urea N,H±CO. — This compound has already been 
mentioned as an example of a diamide (168), and its synthesis 
by the transformation of ammonic cyanate has been explained 
[404]. It is a substance of very great physiological interest. 
It has been found in several of the fluids of the animal body, 
and forms a large constituent of the vitreous humor of the eye. 
With all the higher animals it is the final product of the oxida- 
tion of their tissues, and the chief form in which they are elim- 
inated from the body after having discharged the functions of 
life. It takes its name from the secretion of the kidneys, of 
whose solid constituents it forms by far the largest part, and 
after being voided by the body it is soon converted into car- 
bonic dioxide and ammonia, the two substances which, together 
with water, are the principal food of the vegetable world (481) 
(64). This change is apparently induced by certain highly 
unstable bodies, with which urea is associated in the urine, and 
consi>ts simply in the assimilation of one molecule of water to 
each molecule of urea, thus: — 

N 2 H±CO + H 2 = 2 NII 3 + C0 2 . [555] 

The same change may be produced by strong sulphuric acid 
and by various alkaline reagents, also by heating with water 
alone in sealed tubes to temperatures above the boiling point. 

Urea acts as a feeble base, forming salts with the stronger 
acids, and of these the nitrate, (N 2 H±CO)HNO& and the oxa- 
late, (^^(70)2^(7,04, are the most readily crystallized. It 
also forms definite compounds with several metallic oxides and 
with many salts. In all these cases there is no replacement 
of the hydrogen atoms of the urea ; but its molecules combine 
directly with those of the acid, oxide, or salt, as in the above 
examples. Such a reaction as this, however, is a characteristic 
of an amine (167), and not what we should anticipate of the 
neutral amide of carbonic acid, who-e acid amide forms the 
well-known ammonic carbamate (168) and (174). But, un- 
like a true diamine, one molecule of urea does not neutralize 
two molecules of a monobasic acid, but only one, as in the 
above examples. Hence some chemists do not regard urea as 
the true carbamide, but only, a compound isomeric with it, and 



533 COMPOUND UREAS. [§484. 

the following formula represent possible views of its constitu- 
tion : — 
NHfO-CN- {NTTJifCO NH,NKfChHo NH<-N=CO. 

Amnionic Cyanatc. Caruamide. Urea ? Urea ? 

Against each of these, however, we might urge plausible ob- 
jections, and the simple carbamide formula, which is here 
adopted as a provisional mode of explaining the relations of 
the compound, is not less probable than either of the others. 

In whatever way we may write the symbol of the urea mole- 
cule, its single carbon atom must be directly united to one or 
both of the two nitrogen atoms with which it is associated. 
Hence arises an intimate relationship between urea and the 
compounds of cyanogen, from which it is so readily derived. 
Urea, when heated under regulated conditions, yields besides 
other products both cyanic and cyan u lie acids, thus : — 

N 2 H, CO + AgNO* = Ag- 0- CN + NH,N0 3 . [556] 

Solution of urea evaporated with argentic nitrate. 

6N 2 II 4 CO + G//67 = 2H : fO : fC^ „ + bNH 4 Cl [557] 

Compound of urea and hydrochloric acid heated to 145°. 

3N 2 ff 4 CO = 3 NFL, + H* Of C 3 N 3 . [558] 

Urea heated alone to 150° -170°. 

The last reaction is accompanied by another, in which a con- 
siderable portion of the urea is converted into a compound 
similar to itself called Biuret. 
2N 2 H 4 CO == NH 3 + NA C, 2 , 

Biuret. 

or possibly NH 2 - CO-NH- CONH 2 . 

Biuret ? 

484. Compound Ureas. — The atoms of hydrogen in urea 
may be replaced by various hydrocarbon positive radicals. 
Thus compounds are known in which either one, two, or three 
of the four hydrogen atoms in the urea molecules are replaced 
by ethyl or methyl, but the substitution of the fourth hydrogen 
atom by these radicals has not been effected. Ethyl- urea, di- 
ethyl-urea, and triethyl-urea may be prepared by the action of 
ethylic cyanate on ammonia, ethylamine, or diethylamine re- 
spectively 1 (compare also [409]). Of these bodies diethyl-urea 
is especially noteworthy, because it admits of two isomeric 

1 Ethylic cyanate is without nction on triethylamine, and an analyst of the 
reactions t*b >ve described will show tint there is a difference of condition in 
this case, which rrobab'y ex hins why the fourth atom of hvdr 'gen in urea 
cannot be replaced by this method, which succeeds so well for the first three. 



§ 485.] MONUBEIDES. 539 

modifications (according as it is obtained by the reaction of 
ethylic cyanate on ethylamine or of potassic cyanate on diethyl- 
ammonic sulphate), which may be represented thus : — 

(H, C % BfNy CO-(& CJhJI) (HJfiNy CO(N- C a ff a C 2 H 5 ) 
The first of these when treated with alkalies yields besides 
C0 2 simply ethylamine, the second a mixture of diethylamine 
with ammonia. 

By means of the dyad radical ethylene we can bind together 
two molecules of ur^a into a still more complex group. Thus, 
by the action of cyanic acid on ethylene diamine (167), we 
obtain 

H 2 N-CO-NH- GJIfHN- CO-NH 2J 

Ethyclcne-diurea. 

and by the action of the same reagent on diethyl-ethylene-di- 
amine, or that of ethylic cynate on ethylene-diamine, we ob- 
tain compounds differing from the last only in that two of the 
hydrogen atoms are replaced by ethyl. These compounds 
furnish another example of isomerism, similar to that described 
above, but of a more complex type. When decomposed by 
alkalies, the first yields besides C0 2 a mixture of diethyl-ethyl- 
ene-diamine with ammonia, the second a mixture of ethylene- 
diamine with ethylamine. A graphic representation of these 
reactions will further show that two other isomeric modifica- 
tions of the same compound are also possible ; the one giving, 
under the conditions above mentioned, a mixture of ethylene- 
diamine with diethylamine, and the other a mixture of ethyl- 
ethylene-ditmine, ethylamine and ammonia. 

The properties and reactions of these compound ureas are 
analogous to tho<e of urea itself. They act like feeble amine 
bases, but as a rule they unite less readily with acids than 
normal urea. 

485. Monureides. — The atoms of hydrogen in urea may be 
replaced by acid as well as by positive radicals, and there thus 
results a most remarkable class of compounds, which have all 
the characters of true amides. Those which are formed after 
the type of the single urea molecule are called monurpides, to 
distinguish them from the more complex though similar pro- 
ducts having the type of a doubly condensed urea molecule, 
the divreides. These highly complex bodies, like the simpler 
amides, are acid when the replacing radical contains one or 



540 



MONUKEIDES. 



[§ 485. 



more atoms of oxatyl. Otherwise, they are neutral or feebly 
basic. The monureides may be regarded as formed by the 
union of one molecule of an acid with one molecule of urea, 
accompanied by the elimination of one or two molecules of 
water, a reaction, through which one or two of the hydrogen 
atoms in the urea molecule become replaced by the acid radi- 
cal, thus: — 

CO) CO) 

Ho 2 =C 2 H 2 + H 2 yw 2 — H 2 = Ho-C 2 H 2 \N 2 

Glycol uric Acid. 



Glycollic Acid. 



H 2 ) 

Urea. 



CO 

Ho 2 -C 2 H 2 + H 2 \-N 2 — 2HO 
H 2 ) 



CO) 

= c 2 h 2 o[n 2 

Glycolyl Urea (Hydantoin). 

In like manner we may derive, at least theoretically, the sev- 
eral monureides included in the second and third columns of 
the following table from the corresponding acids included in 
the first column. Monobasic acids can of course yield only 
one derivative, and that must be neutral. Dibasic acids, on the 
other hand, yield two, one acid and one neutral. 



Acids. 


Monureides. 


Monureides. 




— H 2 


— 2H 2 




CO ) 




Ho 2 -CO 


Ho- CO yN 2 




Carbonic Acid. 






Allophanic Acid. 






CO) 


CO ) 


Ho 2 =0,0 2 

Oxalic Acid. 


Ho-C 2 2 \N 2 

Oxaluric Acid. 


c 2 o\n 2 

H 2 ) 

Paraban. 




CO ) 

Ro-c 3 oSn 2 

Alloxanic Acid. 


CO ) 


Ho. f C 3 3 

Mesoxalic Acid. 


c 3 oAjsr 2 

Alloxan. 




CO ) 




Ho-C 2 H,0 

Acetic Acid. 


C 2 H s O [n 2 
H*\ 

Acetyl Urea. 






CO ) 

Ho-C 2 H 2 [N 2 
H,\ 


CO ) 


Ho 2 =C 2 H 2 

Glycollic Acid. 


C 2 B 2 \-N 2 
H 2 \ 




Glycoluric Acid. 


Hydantoin. 



§ 486.] 



DIUREIDES. 



541 



Acids. 



Monureides. 



Hu 2 -C 3 H 2 2 

Malouic Acid. 



Tartronic Acid. 



H-(COCO)-Ho 

Glyoxalic Acid. 



Monureides. 
CO ) 

H 2 \ 



o 3 n 2 o 2 yjsr 2 



Barbituric Acid. 



CO 



Ho-C 3 E0 2 \-JV 2 

Dialuric Acid. 



CO 

H-(CO-CO) 



K 



Allanturic Acid. 



486. Diureides. — These may be regarded as formed by the 
union of a monureide with an additional molecule of urea, 
the combination involving as before the elimination of one or 
two molecules of water. The following are a few examples : — 

CO) CO) CO I „ 

_oTrn—c 2 H 2 f iV * 



Ho-C 2 H 2 VN 2 + H 2 }N 2 

Glycoluric Acid. Urea. 



2H 9 



Glycoluril. 

C 



co) co) co\ N 

H-C 2 oSN 2 -f H, { r N 2 — H 2 = H-C 2 2 f "*< 
"4 ) H 2 ) ffj 

Allanturic Acid. Urea. Allantoin. 

c 

CO) CO) c 

Bo-C 3 H0 2 VN 2 + H 2 VN 2 — 1H 2 = Ho-C 3 H0 2 

H 2 ) H 2 \ H 2 

Dialuric Acid. Urea. Uric Acid. 



CO 
C 3 H 2 2 
H,, 

Barbituric Acid. 



CO ) 

N 2 + H 2 \N 2 
H 2 \ 



2JL0= aH,o 



Urea. 




542 UMC ACID. [§487. 

It must not be inferred that the equations either of this or of 
the last section represent actual processes by which the various 
urides have been prepared. They merely indicate the most 
probable theory in regard to the constitution and chemical re- 
lations of these bodies which we have been able to form. The 
substances themselves are either products of the animal organism, 
or else have been prepared from such products by different chem- 
ical processes, and our only knowledge in regard to their mo- 
lecular structure has been derived from a study of their prop- 
erties, and of the chemical changes in which they are formed 
or broken up. For the evidence on which the rational sym- 
bols here given are based we refer the student to the memoirs 
of Baeyer, in the Annalen der Chemie und Pharmacies contain- 
ing the results of his very extended investigations of this class 
of compounds. 1 

487. Uric Acid is not only the most important of the ureides, 
but it is the source from which almost all the rest have been 
derived. It is a constant product of the animal organism, re- 
sulting from the imperfect oxidation of the nitrogenized tissues. 
With the reptiles, birds, and insects it forms (in combination 
with ammonia) the chief part, and in some cases nearly the 
whole, of their solid excrements ; but in mammalia the oxidation 
proceeds further in the body and the product voided is princi- 
pally urea. Nevertheless, uric acid is always present in human 
urine, and in certain abnormal states of the system the amount 
becomes increased to an injurious extent, giving rise to sedi- 
ment, gravel, or calculi. In some forms of gout all the fluids 
of the body become saturated with it, and in combination with 
soda it is deposited in the joints, forming what are familiarly 
known as chalk stones. 

Uric acid, when pure, forms a white crystalline powder, 
which under the microscope exhibits definite and character- 
istic crystalline forms ; but the crude acid is more or less tinted 
by the coloring matter of the urinary secretion, from which it 
is prepared. When heated, it decomposes without melting, 
yielding a sublimate of cyanuric acid, ammonic cyanate (or 
urea), and ammonic carbonate, leaving a carbonaceous residue 

1 See, also, an article in Silliman's Journal, vol. 96, page 289, by Dr. W. 
Gibbs, in which rational symbols for these bodies are theoretically deduced 
from either the known or assumed polymeric forms of cyanic acid. 



§487.] URIC ACID. 543 

behind. It is almost insoluble in water and the dilute mineral 
acids; but it dissolves readily in alkaline solutions, since it 
forms with the alkaline radicals more or less soluble salts. It 
also forms salts with several of the more basic metallic rad- 
icals, which may either replace one or two of its typical hydro- 
gen atoms. We have, therefore, in several cases both an acid 
and a basic salt of the same radical. But while we can only 
replace two of the hydrogen atoms with metallic radicals we 
can replace three with ethyl. 

The rational formula of uric acid ha 5 ? already been given. 
It is based chiefly on the following coih-iderations. When the 
acid is treated with a mixture of hydrochloric acid and potas- 
sic chlorate (a strong oxidizing acid), it is converted wholly 
into a mixture of alloxan and urea, 

2T 4 ff 4 C 5 3 + + Hfi = N 2 ff. 2 C 4 4 + NJJ 4 CO. [559] 

Uric Acid. Alloxan. Urea. 

Now the first effect of the oxidation would be naturally to re- 
move the hydrogen atoms from the hydrocarbon radical we 
have assumed to exist in uric acid, changing it into the hypo- 
thetical compound N 4 H. 2 C 5 3 , and then this, by absorbing two 
molecules of water, gives at once alloxan and urea. 

C\ C\ 

C{ c[ CO) CO) 

Ho-C z H0 2 C N 4 C s O, f iV 4 -f 2H 2 = C 3 3 }■ N 2 + H > N a . [560] 

Uric Acid. Hypothetical Intermediate. Alloxan. Urea. 

Further, when alloxan is boiled with an alkaline solution it 
yields urea and the mesoxalate of the alkaline radical. Lastly, 
mesoxalic acid is a crystalline solid resembling oxalic acid, and 
like it is dibasic. As its composition is well determined there 
can be no question that it contains the radical (7 3 3 , and is the 
third term of a series of which carbonic acid and oxalic acid 
are the other three. 

Ho 2 =CO Bb 2 =G 2 2 BbfC 8 Op 

Carbonic Acid. Oxalic Acid. Mesoxalic Acid. 

This completes the chain of evidence, but the student will not 
fail to see that it has a weak point. 

The view of the constitution of uric acid here adopted is 
further supported by a reaction observed by Strecker, who 
found that, when treated with hydriodic acid, one molecule of 
uric acid breaks up into one molecule of glycocoll {Ho,NH 2 = 



544 



URIC ACID. 



[§ 487. 



C 2 H 2 0), three molecules of ammonia and three of carbonic di- 
oxide. Now if uric acid contains, as we have assumed, the 
tartroriyl radical, it must have the graphic symbol given below, 
leaving the parts in brackets undeveloped (473), and by coin- 
paring this with the symbols of tartronic acid and glycocoll on 
either side, it can readily be seen that the products are pre- 
cisely such as might be expected from the action of the reagent 
used, assuming of course that our theory is correct. 

OHO OHO OH 

Ho-C-C-C-Ho (NH 2 )-C-ab-(N z C 2 ) {NH 2 )-b-b-H. 



Ho 

Tart onic Acid. 



Ho 

Uric Acid. 



Ho 

Glycocoll. 



Uric acid is remarkable for the facility with which it is al- 
tered by oxidizing agents, and for the great number of definite 
and crystallizable compounds obtained, either in this manner or 
by treating the immediate products of oxidation with various 
reagents. The following list includes all the more important 
derivations : — 

Derivatives of Uric Acid, iV 4 ^ 4 C 5 3 . 



Allantoin, 


N<H,C<O z 


Hydantoin, 


N 2 H<C 3 2 


Allanturic Acid, 


N t H A C z O z 


Hydurilic Acid, 


N&CA 


Alliturc Acid, 


NJU C A 


Leucoturic Acid, 


NAAA 


Alloxan, 


*AAA 


Mesoxalic Acid, 


H 2 C 3 6 


Alloxnnic Acid, 


NM,C A O h 


Murexide, 


N,H 6 C B 0, 


Alloxantin, Nfl^A- 3H 2 


Mycomelic Acid, 


NJSfiA 


Barbituric Acii, 


N&C& 


Oxaluric Acid, 


^AAO, 


Bromo-barbituric ) 
Acid, I 


Br 


Paraban, 


n 2 h 2 c 3 o 3 


N&fifi, 


Pseudo-uric Acid, 


NfiAA 


Dibromo-barbituric } 


Br 2 


Sfrypbnic Acid, 


N.H.C.O, 


Acid, J 


NJJ 2 C,0 3 


Thionuric Acid, 


N a HAOj 


Dibarbituric Acid, 


njoaa 


Uramil, 


NA£A 


Dialuric Acid, 


N t Hfifit 


Urinilic Acid, 


NfiAA 


Bilituric Acid, 


N&C& 


Uroxanic Acid, 


NJhAA 


Glycol uric Acid, 


N o H 6 C 3 3 


Violantin, 


NACA 


Glycoluril, 


N\H % Cfi t 


Violuric Acid, 


N&Cfl't 


Hydantoic Acid, 


N 2 H 6 C 3 3 


Xanthine, 


NACA 



It must not be supposed that the term acid, used in connection 
with so many of these compounds, implies that they all have 
the constitution of true organic acids, that is, contain one or 
more atoms of oxatyl. That there are among them true acid 



§487.] URIC ACID. 545 

amides (168) lias already been shown, but in most cases the 
apparent acid reaction arises from the power, which many 
amides possess, of exchanging one or more of their atoms of 
typical hydrogen for the basic radicals of metallic hydrates, 
and this relation undoubtedly shows that the molecules of these 
bodies are in a polar condition not unlike, although less marked, 
than that of the true acid molecules of the water type. 

For the various processes by which the uric acid derivatives 
have been prepared we must refer the student to Watt's Dic- 
tionary of Chemistry, from which, with some alterations, the 
above table has been taken. But in spite of the apparent com- 
plexity of the results, the chemical changes involved in the 
production of these bodies may be referred to a few types. 
We may have : — 

First. The breaking up of a diureide into a monureide and 
urea. 

) CO ) CO } 

cjw \& + H *° = °* a *° [ w * +^ 2 f $ E 361 l 

jj \ Ha) H 2 ) 

-"4 ' Hydantoin. Urea. 

Glycoluril. 

By boiling a solution of glycoluril with acids, and the reaction [560] given 
above is an example of a similar change. 

Secondly. The formation of a biureide from a ureide. 

2N 2 H 2 C 4 4 — = N 4 H 4 C,0 7 . [562] 

Alloxan. Alloxantin. 

By the ac'ion of hydric sulphide or nascent hydrogen on a solution of alloxan. 
Thirdly. A modification of the more complex radical of the 
ureide, without altering its relations to the compound. 
CO) CO) 

o 3 o 3 [n 2 + o = c 2 o» yjsr 2 + co 2 [563] 

B % ) H 2 ) 

Alloxan. Paraban. 

By genily warming alloxan with nitric acid. 

N 4 H 4 C,0 3 +0 + H 2 = N 4 H Q C 4 O z + C0 2 . 

Uric Acid. Allantoin. 

By boiling uric acid with water and plumbic dioxide. 

N 4 H,C 4 3 + ff 2 = N 4 H,C 4 2 +H 2 0. [564] 

Allantoin. Glycoluril. 

By the action of sodium amalgam on a solution of allantoin. 

CO) CO) 

C 2 H 2 BrO V N 2 + HBr = C 2 H 2 [ JV 2 [565] 

H.) H 2 \ 

Bromacetyl Urea. Hydantoin. 

By the action of ammonia. 



546 ALLANTOIN AND MUREXIDE. [§488. 

CO) CO) 

C 8 H 2 9 [N~ 2 — H + N0 % = C 3 H(N0 2 ) 0, VN 2 [5G6] 
H 2 ) H 2 \ 

Barbituric Acid. Nitrobarbit"ric or 

Dilituric Acid. 

By the action of nitric acid. 

CO) CO) 

0,0, { r N 2 + H 2 = Ho-C 3 OAN 2 [567] 

B 2 \ H 3 \ 

ALoxan. Alloxanic Acid. 

Fovrtlily. A breaking up of the ureide into ammonia and 
the hydrate of its principal radical. 

CO) 

C 3 (K VN 2 + 3H 2 = C0 2 + Ho>f C 3 0, + 2NH 3 [568] 



HA 



Mesoxalic Acid. 



CO 
C 3 H 2 OAlSr 2 + 3H 2 = C0 2 + HofC 3 H 2 0, + 2NH 3 [569] 

TT V Malonic Acid. 

Barbituric Acid. 

By heating with solutions of causMc alkalies. 
It will, of course, be understood that in the actual processes 
two or more of such reactions as have been here illustrated 
may concur or may succeed each other. Indeed, it has been 
found very difficult to isolate them. 

488. Allantoin and Murexide are the only bodies among 
the uric acid derivatives which have any other interest than 
that which is connected with their chemical composition, and 
the only special interest attaching to allantoin arises from 
the isolated fact that it appears to be an essential constituent 
of the allantoic liquid. Murexide, however, is a most brilliant 
purple pigment, and before it was superseded by the aniline 
colors was manufactured on a large scale. It can be readily 
prepared by adding ammonia to the solution of alloxan and 
alloxantin, which is obtained by dissolving uric acid in dilute 
nitric acid under regulated conditions, and the production of a 
purple color under such circumstances is a delicate test for uric 
acid. Murexide crystallizes in brilliant garnet-colored prisms, 
which appear gold-green by reflected light. It gives with wa- 
ter a rich purple solution, but is insoluble in alcohol or ether. 
It appears to be the ammonium salt of a very complex amide, 
which has been called purpuric acid ; but although the ammo- 
nium radical may be readily replaced by various metals the 



§489.] GUANINE AND GUANIDINE. 547 

amide itself has not been isolated, and our knowledge in regard 
to these beautiful compounds is as yet too limited to enable us 
to assign to them any probable rational symbols. Similar pro- 
ducts are obtained by the action of potassic cyanides on picric 
acid (457), and these isopurpurates, as they are called, are 
isomeric with the corresponding uric acid derivatives. 

489. Guanine and Guanidine. — The first of these com- 
pounds resembles uric acid, and is found associated with it in 
some kinds of guano, but it forms an amorphous instead of a 
crystalline powder, and has basic rather than acid relations. 
Ultimate analysis gives the empirical symbol H 5 N 5 C 5 0, and it 
may be regarded as derived from xanthine by replacing the 
radical HO by H 2 N, — a view of its constitution which is sus- 
tained by the fact that when treated with nitrous acid it yields 
that well-known diureide, 

2ff 5 N,C 5 0+0-0 = 2C 5 ff 4 N 4 0,+ II 2 + ]V^. [570] 

Guanine. Xanthine. 

An equally interesting reaction is obtained by digesting guanine 
with a mixture of hydrochloric acid and potassic chlorate, when 
it breaks up into paraban and a remarkable amine called 
guanidine. 

H 6 N,C,0 + H 2 + 0-0 = 

Guamne - H b N,C+ J7 2 K 2 3 3 + C0 2 . [571] 

Guanidine. Paraban. 

There are also formed at the same time, although in smaller 
quantities, xanthine, oxaluric acid, and urea. 

Guanidine is a crystalline solid having a strong basic reac- 
tion, absorbing C0 2 from the air, and forming with acids crys- 
talline salts, which, like H- N 3 • HCl, contain for every mole- 
cule of a monobasic acid one molecule of the amine. It can 
be formed synthetically by heating iodide of cyanogen with an 
alcoholic solution of ammonia in a closed tube, and this reac- 
tion leaves no doubt in regard to its molecular structure. 

MC-I+ 2H 3 N= HfrC=(NH 2 ) 2 . HI. [572] 

Guanidine has also been obtained by heating with the same 
solution, and under similar conditions, chlorpicrin, a product of 
the action of chlorine on picric acid. 

OCk(N0 2 ) -f ZNH % = 
chiorpicrin. jj^ c § HCI _|_ 2 HCl + HNO s . [573] 



548 GLYCOCYAMIN AKD GLYCOCYAMIDINE. [§ 490. 

The interpretation of this reaction is aided by the fact that 
when the same chlorpicrin is distilled with alcohol and sodium 
it yields an ether which is a true ortho-carbonate, thus : — 

0==CI 3 ,(WO,) + 4JVa-0-C 2 ff 5 — 

( C 2 H 5 ) 4 = <9 4 = C + ZNa CI + NaN0 2 . [574] 

The same ether, heated with aqua ammonia in a closed tube, 
gives guanidine. 

Etf o 4 = C + 3JSTR 3 = ±Et- OH -f HN= C-(NH 2 \. [575] 
There are also known a number of well-marked amine bases, 
which may be regarded as derived from guanidine by replacing 
one, two, or three atoms of its typical hydrogen by hydrocar- 
bon radicals. 

490. Glycocynmin and Glycocyamidine, Creatine and Crea- 
tinine. — By passing chloiide of cyanogen and ammonia gas 
simultaneously into anhydrous ether, the ammonic chloride 
which is formed separates out, while there remains in solution 
one of the simplest and at the same time most remarkable 
compounds of the amide group. 

CN- CI + 2NH, — NH. 2 - CN + NH, CI [576] 

Cyanamide. 

Now we can directly unite the cyanamide thus formed with 
glycocoll, and the product is called glycocyamine, which when 
acted upon by dry HGl yield an allied base called glyeocyami- 
dine. The constitution of these bodies can be inferred with 
great certainty from the simple synthetical process by which 
the first is formed, interpreted by reactions [572] and [576]. 
It will be noticed that the factors in these two reactions are 
nearly the same, and the difference in the products depends on 
slight variations of conditions. Indeed, guanidine may be ob- 
tained by the action of NH$ on the chloride as well as on the 
iodide of cyanogen, only it is not then the chief product, for 
the reaction tends to take the form of [576] rather than of 
[572]. An analysis of these reactions will show that the dif- 
ference in the results depends on the circumstance that, while 
in [572] the two atoms in the cyanogen radical remain united 
by the three original bonds, in [576] one of these bonds is let 
loose, forming points of attachment to which the two radicals 
^Tand NH 2 join themselves. Now the union of glycocoll with 
cyanamide probably depends on a similar change, so that in 



§490.] CREATINE AND CREATININE. 549 

the resulting glycocyamine the two atoms in the original cya- 
nogen radical remain joined by two bonds, while the two parts 
of the glycocoll molecule, NH t and HO-C 2 H 2 0, unite to the 
points of attachment which the breaking of the third bond fur- 
nishes. The subsequent production of glycocyamide is simply 
an example of the change from a monad to a dyad radical by 
the elimination of HO with which we are so familiar (485). 

The interest attaching to the above compounds arises from 
the fact thaf there is found in muscular juice a crystalline base 
called creatine (supposed to have important physiological rela- 
tions), which is the first homologue of glycocyamine, and which 
yields, when treated with acids, a second base, creatinine, that 
is the first homologue of glycocyamide. Thus we have the 
following; triamidcs : — 



II, S " 




C 2 H 2 [N, 


B*) 


H,) 


Guanidine. 


Glycocyamine. 


Glycocyamidihe. 




C ) 


) 




Ho-C 2 H 2 l„ 






4) 


H 2 ) 




Creatine. 


Creatinine. 



Both creatine and creatinine have been found not only in mus- 
cular flesh, but also in the urine, in the blood, and in other ani- 
mal fluids ; but it is difficult to determine to what relative 
extent they exist in the living body, since, while strong acids 
convert creatine into creatinine, alkaline reagents change crea- 
tine back to creatinine, and these changes may take place in 
the processes of extraction. These bases unite directly with 
acids, forming well-crystallized salts, and one molecule of base 
neutralizes in each case one molecule of a monobasic acid. 

Creatine has been formed synthetically by a process which 
plainly indicates its molecular constitution ; for as glycocya- 
mine results from the union of cyanamide with glycocoll, so 
creatine is the product of the union of cyanamide with methyl- 
glycocoll, a compound usually called sarcosine, and the reac- 
tions below, which show that sarcosine is really methyl-glyco- 
coll, complete the evidence. 

1st. Synthesis of glycocoll. 
Ho-( C 2 H 2 0) : CI + &Hs = Ho-{ C 2 H 2 0)-N=H 2 + HOI [577] 

Chloracetic Acid. Glycocoll. 



550 CAFFEINE AND THEOBROMINE. [§ 492. 

2d. Synthesis of sarcosine. 
Ho-{C 2 H 2 0)-Cl + m CR,)M 2 =: 

Methylamine. 

Ho-{ C 2 H 2 0)-JV=( CH & ),H+ HCl [578] 

Sarcosine. 

491. Caffeine and Theobromine. — These well-known or- 
ganic bases which are regarded as the active agents in tea and 
coffee on the one hand, and in the cacao-bean on the other, are 
closely allied to the class of compounds we have been studying. 
They are probably the methyl substitution products of a sim- 
pler amide not yet discovered. That caffeine is methyl-theo- 
bromine there is no doubt, for theobromine can be converted 
into caffeine by a simple process of substitution. It is also 
probable that theobromine itself contains methyl, for when 
caffeine is oxidized by chlorine and water it yields well-known 
dimethyl products. Moreover, these products are the methyl- 
ated forms of two well-known uric acid derivatives, viz. allo- 
xanthine and paraban, indicating that caffeine and theobromine 
are allied to the diureides. Now it appears from their empiri- 
cal symbols that theobromine differs from xanthine by just 
(CH 2 \ thus: — 

C 5 H 4 N 4 2 C 7 ff 8 ¥ 4 2 C s R w JST 4 2 . 

Xanthine. Theobromine. Caft'eiue. 

But theobromine can not be simply dimethyl-xanthine. for this 
last compound has been made, and although isomeric with xan- 
thine is not the same substance. When caffeine is treated 
with barium hydrate there is formed during the first stage of 
the process a new base called caffeidine, but this is subsequently 
decomposed, and the ultimate products of the reaction are, be- 
sides carbonic dioxide and ammonia, formic acid, methylamine, 
and sarcosine. Creatine similarly treated yields, besides car- 
bonic dioxide and ammonia, only sarcosine, and these reactions 
indicate that the unknown amide, of which coffeine is a methyl- 
ated substitution product, is allied to creatine, probably con- 
taining like this the glycol radical. 

492. Vegetable Alkaloids. — The active principles of many 
medicinal or poisonous plants are crystallizable bodies, which 
closely resemble in their general properties and chemical re- 
lations the complex amines or basic amides we have been study- 
ing. Several of them, like quinine and morphine, are well- 
known articles of the materia medica, and are perhaps the 



§ 492.] VEGETABLE ALKALOIDS. 551 

most valuable medicinal agents which we possess. As a gen- 
eral rule they are soluble in water, have a strong, bitter taste, 
and form well-marked crystalline salts with acids. Hence the 
name of vegetable alkaloids. The number of these bodies 
now known is exceedingly large. The dried juice of the 
poppy, which we call opium, alone contains not less than eight 
distinct bases. Two of the alkaloids, conine and nicotine, 
from the hemlock and tobacco plant respectively, are volatile 
oily liquids^ and they do not contain oxygen. The great body, 
however, of the alkaloids are oxygenated compounds and can- 
not be distilled without decomposition. These two classes of 
alkaloids correspond to the volatile amines on the one hand, 
and the non-volatile ammonium bases on the other; but no safe 
conclusion in regard to their constitution can be drawn from 
this seeming analogy, for not only are the facts we have been 
studying sufficient to show that the class of amines or alkaline 
amides includes many non-volatile oxvgenated ba>es, but all 
the natural alkaloids combine directly with acids in forming 
salts. Moreover, in several cases we are able to substitute 
hydrocarbon radicals for one or more of the hydrogen atoms of 
the alkaloid, and obtain bodies which, like the ammonium bases, 
eliminate water when they combine with acids. 

Among the most important of the vegetable alkaloids may 
be mentioned morphine, narcotine, and codeine from opium ; 
quinine and cinchonine from cinchona bark ; strychnine and 
brucine from nux-vomica and other strychnos plants ; aconi- 
tine from the monkshood ; atropine from belladonna and stra- 
monium ; veratrine from the white hellebore. All these sub- 
stances have been carefully studied, and their general properties 
and chemical relations are accurately known. Their empirical 
formulas show that with few exceptions they must be very 
complex bodies, but beyond this very little has been made out 
in regard to their chemical constitution. In several cases the 
number of replaceable atoms of hydrogen have been deter- 
mined, and in others the natural alkaloid has been proved to 
be a methylated substitution product of a simpler base, but in 
no case has the molecular structure been fully developed. The 
great difficulty encountered in investigating the constitution of 
these bodies arises from the fact that we know of no reagent 
by which we can replace nitrogen by monad radicals, and thus 



552 AMINE-AMIDES, OR ALKAMIDES. [§493. 

break up the alkaloid into the several atomic groups of which 
it consists, without decomposing the radicals also. The student 
should study in this connection the important investigation of 
Matthiessen 1 on morphine and codeine, and that of Schiff 2 . on 
conine, the first alkaloid which has been produced synthetically. 
493. Amine- Amides, or Alkamides. — It niu.-t have been 
noticed that with the complex compounds we have been re- 
cently studying, the clear distinction between amines and 
amides previously drawn (167, 1G8) is almost wholly obscured. 
The effect of introducing several radicals, both acid and basic, 
into the same ammonia group, cannot be traced to any general 
principle. The resulting molecule has sometimes basic and 
sometimes acid relations. Hence it is that we have been 
obliged to class with the amides so many substances having 
well-marked alkaline properties, and for this reason many 
chemists distinguish a third class of compounds under the am- 
monia type, to which they give the name of amine-amides or 
alkamides (alkaline amides). An alkamide is frequently de- 
fined as a compound of the ammonia type, in which the hydro- 
gen atoms are in part replaced by basic and in part by acid 
radicals; but we prefer to give to the term the simple meaning 
which the derivation indicates, for urea, which contains only an 
acid radical, is one of the best-defined bodies of the class, at 
least if we accept the view of its constitution usually taken. 
The distinction has not been before made in this bonk, because 
the study of the alkamides cannot well be separated from that 
of the true amides to which they are so closely related ; and 
since several of the more important of these compounds have 
already been described, further examples are unnecessary. 

1 Proceedings of the Royal Society of London, XVII. 455 ; also, Ann. 
Chem. und Pharm., VII. Supplementbar'd, 170. 

2 Berichtc der Deutschen chem., Gesellschaft, Jahrgang, III. 946, 



§494] ALCOHOLS AND THEIR DERIVATIVES. 553 



Alcohols and their Derivatives. 

494. Chlorals. — The white solid which is the ultimate re- 
sult of the action of chlorine gas on ab.-olute alcohol is a com- 
pound of alcohol with one of its chlorinated derivates called 
chloral. When the crude product of this reaction is treated 
with strong sulphuric acid the chloral separates out, and may 
be decanted and purified by repeated distillation over lime. It 
is a thin colorless oil, having a pungent odor and astringent 
taste, boiling at 98°6, with Sp. Gr. = 1.49 and Sp. Gr. = 
74.04. It readily dissolves in water, yielding a neutral solution 
which does not precipitate nitrate of silver, but in so dissolving 
it enters into combination, and if the amount of water is small 
the union is attended with a marked elevation of temperature. 
If the amount taken is about one eighth of the weight of the 
chloral the whole mass solidifies, and the white translucent solid 
thus formed is the familiar preparation which is now so highly 
valued as an anesthetic agent. Chloral Hydrute has a strong, 
pungent, ethereal odor, volatilizes gradually in the air, and dis- 
tils without decomposition when heated. It melts at 50° to 51°, 
boils at 97° to 99°, has Sp. Gr. = 1.61 and Sp. Gr. = 39.84, 
showing that chloral and water are disassociated at 100°. This 
substance was discovered by Liebig in 1832, but it is only re- 
cently that its valuable medicinal qualities have been appreci- 
ated or its chemical relations fully understood. 

Chloral is a chlor-aldehyde, and has the same structure as 
acetic aldehyde, but contains Cl 3 in place of the H z in the 
methyl radical. 

CHzCO-H CCh-COH. 

Acetic Aldehyde. Acetic Chloral. 

Its constitution is shown by the following reactions : 1st. 
Acetic aldehyde when acted on by chlorine gas, under regu- 
lated conditions, is converted into chloral. 2d. Chloral when 
acted on by nascent hydrogen changes back to aldehyde. 3d. 
Chloral combines with NH& forming a compound correspond- 
ing to aldehyde ammonia. 4th. Oxidizing agents convert chlo- 
ral into chloracetic acid (31) and [479]. 

When chloral or its hydrate is treated with a solution of 
a caustic alkali it yields chloroform, together with a formiate 
24 



554 CHLORALS. [§ 494. 

of the alkaline metal, and the value of the hydrate as an 
anesthetic agent seems to depend on the fact that a similar re- 
action takes place in the blood. 

( COkY CO-IT + (K- 0)-II= K- 0-( CO-H) + CC1,-H. [579] 

Chloral. Fotassic Formate. Chloroform. 

When chloral is heated with nitric acid there is formed, be- 
sides chloracetic acid, which is the direct product of the oxida- 
tion due to this reagent, also a small amount of a substance 
called ehlorpicrin. The last is the product of a metathesis be- 
tween the radicals of the acid and the chloral, thus : — 

(CC!,)-CO-H+ (H-OyNO,= 

chiorai. H-Ch{CO-H) + CCh-{NOi). [580] 

Formic Acid. Chlorpicrin. 

It will be noticed that while in this reaction the radical CCI 3 
changes place wiih HO, in the previous reaction it changed 
place with KO, and this fact is a most striking illustration of 
the theory of chemical polarity. Chlorpicrin is an oily liquid, 
usually obtained by the action of chlorine on picric acid, and 
may be regard.nl as chloroform in which the remaining hydro- 
gen atom has been replaced by N0 2 - 

Chloral combines not only with water and with ethylic al- 
cohol, but also with other alcohols of the same family, with 
urea, and with several amides. These products are generally 
regarded as molecular compounds, but it is more probable that 
they have the constitution represented in the scheme below : — 

(CFI,-CH)-0 (CCh-CH)-O. 

Acetic Aldehyde. Chloral. 

(CCl 3 -CH)=JTo 2 . 

Chloral Hydrate. 

{CCk-CHyEto<Ho. 

Chloal Hydro ethylate. 

( Off,- CH)-Eto 2 ( CC1* CH )=Eto 2 . 

Acetal. Chloral Diethylate. 

As here represented, the compounds, with water and alcohol, 
are intermediate terms between chloral and another substitution 
product, which bears the same relation to acetal 1 that chloral 

1 Acetal is a well-known product of the ox ; dation of ethvlic aVohol. It 
contains the radical ethvlldene, a d differs both in Sp Gr. and boiling-point 
from an isomeric compound containing ethylene, which has also beeu isolated. 






§495.] MELLITIC ACID. 555 

bears to acetic aldehyde. These formulae are supported by the 
fact that, while aldehyde chloral and chloral hydrate are all 
converted by PCl 5 into ethylidene chloride (31) (464), the 
compound of chloral with alcohol yields, under the same condi- 
tions, a substance represented by the symbol ( GOl^CHyEto, 01, 
and not the normal products of the action of POl 6 on chloral 
and alcohol separately, as we should expect if they were pres- 
ent as such in the compound in question. 

It has been stated above that acetic chloral may be formed 
from acetic aldehyde by the direct action of chlorine gas un- 
der regulated conditions. It is simply necessary that there 
should be present with the aldehyde lumps of marble to absorb 
the HCl, which is formed by the reaction ; for HOI converts 
acetic aldehyde into crotonic aldehyde, and this product is then 
the only point of attack for the chlorine gas. Thus it is that 
when chlorine acts on acetic aldehyde without any check, the 
final product is not acetic chloral, but a new chloral derived 
from crotonic aldehyde (453). 

( oh s - oh off- coy h ( cch- off- oh- coy II. 

Crotonic Aldehyde. Crotonic Chloral. 

Crotonic chloral resembles outwardly acetic chloral, and 
forms a similar compound with water. It is the only other 
chloral which has thus far been isolated ; but an insoluble iso- 
meric modification of common chloral is known whose relations 
are not yet understood. 

495. Mellitic Acid. — This compound has long been known 
as a constituent of the mineral mellite or honeystone, which 
is mellitate of aluminum, [Al 2 ]C 6 6 . 9H 2 0, and is found in 
reddi>h-vellow octahedral crystals in the brown coal at several 
localities ; but it is only recently that its remarkable chemical 
relations have been discovered. It has been shown by Bayer 
that this acid is hexabasic and belongs to the phenyl group. 
It may be regarded as derived from benzol, C & H^ by replacing 
all the six atoms of hydrogen with oxatyl. Benzoic acid, it 
will be remembered, is benzol with one of the hydrogen atoms 
replaced by oxatyl, and Bayer has not only been able to iden- 
tify three of the four intermediate acids which are theoretically 
possible, but he has also shown that each of the three is capa- 
ble of two isomeric modifications. Thus we have : — 



556 MELLITIC ACID. [§ 495. 

Normal Series. Isomeric Series. 2d Isomeric Series. 

Benzol. Q.Ha- 

Benzoic Acid. QH r (CO-Ho). 

Terephthalic Acid. Isophthalic Acid. Phthalic Acid. C u Hf{ CO-Ho) y 

Triuiellitic Acid. Trhnesic Acid. Ileiniuieliiric Ac^d. C H^(CO Ho) 3 . 

Pyroniellitic Acid. Preunitie Acid. Meilopiiauic Acid. C r ,H.M CO-Ho)^ 

C ri H~l(CO-Ho) s . 
Mellitic Acid. C G vi ( CO-Ho) 6 . 

The isomeric modifications probably result from a variation of 
the order in which the hydrogen and oxatyl atoms are attached 
to the carbon atoms of the primary nucleus (428, Fig. c.) and 
(456). 

One of the compounds included in the above scheme has 
certain other remarkable chemical relations which point with 
great certainty to its molecular constitution. Phthalic acid 
is not only a derivation of benzol, but also of naphthaline; 
for this well-known hydrocarbon (434), when heated with 
strong oxidizing agents, yields a mixture of phthalic and oxalic 
acids. Assuming it proved that phthalic acid has the benzol 
nucleus, the best theory we can form in regard to this reaction 
gives to the molecule of naphthaline the singular constitution 
represented below; and it can be seen by comparing the three 
graphic symbols placed side by side that the reaction is thus 
fully explained. 







H 


H 

0, 

G 


H H 

H \<5\ A ,h 

P \ G G 


H 

A A .R 
0^0 


<7 v 


,G / G G 


G G 

* c' V > 


H 


H H 


H 


Oxalic Acid. 


Naphthaline. 


H 

Phthalic Acid. 



If this theory is correct, it follows that in phthalic acid the 
two oxatyl groups are united to adjacent carbon atoms of the 
nucleus, and that its constitution is so far determined. Again, 
it will be noriced that these adjacent carbon atoms are united 
by a double bond, and that in the closed chain, of which they 
are a part, the links are joined by double and single bonds al- 
ternating. Now it is evident that if either of these double 
bonds could be exchanged for a single one, the nucleus would 



§ 195.] MELLITIC ACID. 557 

be able to attach to itself two additional hydrogen atoms, six 
in all, and that if, besides, we could break the chain between 
the two adjacent atoms above referred to, the nucleus could 
hold yet two more, and we should then have suberic acid (470). 
Now all the-e transformations appear to be possible, for we 
have been able to prepare the following series of bodies : — 

Phthalic Acid, C 6 //f ( CO-Ho) 2 . 

Hydro-phthalic Acid, <7 6 # (! =( CO~Ho) 2 . 

Tetrahydro-phthalic Acid, C G ff 8 =(CO-JIo) 2 . 

Ilexahydro-phthaiic Acid, C ii H 10 =(CO-Ho) 2 . 

Suberic Acid, C f 6 II 12 =( CO-Hu) 2 . 

We are also acquainted with still another derivative of benzol 
called tartro-phthalic acid, which differs from hexahydro-phtha- 
lic acid only in that there is associated with each oxatyl group, 
and attached to the same carbon atom, HO in place of H. 
Tartro, hexahydro, and tetrahydro-phthalic acids are related 
by a peculiar kind of homology to tartaric succinic and maleic 
acids respectively, which will be evident on bringing together 
their graphic symbols. The theory that in all these acids ex- 
cept suberic the two oxatyl groups are joined to adjacent car- 
bon atoms is sustained by other considerations than the one we 
have given here, but for these we must refer the student to the 
original memoirs. 

The graphic symbol of naphthaline being so symmetrical, it 
would seem impossible to determine on which side the division 
of the nucleus takes place in the reaction represented above \ 
but there are conditions in which even this can be traced. We 
have written below the symbol of naphthaline so as to indicate 
in a measure its bilateral structure, and on the same line we 
have given the symbols of two of its well-marked substitution 
products, which are very numerous : — 

C 4 H 4 =CfC 4 H 4 C 4 ff 4 =C 2 =C 4 C! 2 2 C 4 H,CbC 2 =C 4 Cl 4 . 

Naphthaline. Dichlordioxynaphthaliue. Pentachlornaphthaline. 

Now the first of these derivatives when oxidized gives phthalic 
acid like naphthaline itself, while under the same conditions the 
second gives tetrachlorphthalic acid. Evidently, then, in the 
first case the substitution is confined to one side of the naphtha- 
line molecule, and the division which accompanies the oxida- 
tion takes place on the same side ; while in the second case not 



558 mellitic Acid. [§ 495. 

only all the hydrogen atoms on one side are replaced, but also 
one on the other, and the division takes place on the side of the 
single chlorine atom ; for were the nucleus divided on the other 
side we should have not tetrachlorphthalic but monochlorphthalic 
acid. These reactions, moreover, furnish very strong evidence 
in favor of the theory of the structure of the naphthaline mole- 
cule stated above. Since, as we obtain a body having the 
structure of phtlialic acid on whichever side we divide the 
molecule, it is evident that the two sides must have the same 
structure, so that if we are not mistaken in regard to the struc- 
ture of phthalic acid there can remain but little doubt in 
regard to that of naphthaline. Now phthalic acid, when heated 
with an excess of lime, yields benzol, and benzol, when oxi- 
dized under certain conditions, yields benzoic and phthalic 
acid, reactions which may be almost said to prove that this 
acid contains the benzol or phenyl nucleus. The simple rela- 
tions of phthalic to benzoic acid are evident. 

If, with Kekule, we number the carbon atoms of the phenyl 
nucleus from 1 to 6, and assume that in phthalic acid the two 
oxatyl radicals are united to the first and second atoms of the 
nucleus, then it is evident that, without altering the general 
structure, two modifications of it may be obtained by changing 
the position of the oxatyl radical, which can also be attached 
either to the first and third or to the first and fourth atoms of 
the closed chain. Now there is good reason for believing that 
such is the position of the radicals in isophthalic and tere- 
phthalic acids respectively, but for the evidence we must refer 
to the original papers. 1 

1 Ann Chem. und Pharm., VII. Supplementband, 1; also CXLIX. 27 ; also 
Jour. Chem. ISoc. of London, Vol. IX. 372. 



§ 49C] QUINONE. 559 



Quinone Group. 

49G. Quinone. — The artificial production of alizarine, the 
coloring principle of madder, is not only one of ihe most re- 
markable achievements of modern chemistry, but is also a 
direct corroboration of the validity of the mode of reasoning 
which the new philosophy of the science has introduced. Ali- 
zarine was actually constructed by following out the indications 
of a theory of its molecular structure, to which a study of its 
reactions and those of allied compounds had led. In order to 
make clear the course of the investigation we must go back to 
the discovery of quinone in 1838. This body was obtained 
by the oxidation of quinic acid, a vegetable acid found in cin- 
chona bark, where it is combined with cinehonine and quinine. 
Quinone is a volatile solid, crystallizing by sublimation in 
shining yellow needles, which have the composition indicated 
by the empirical symbol GqH^O^. When heated with a mix- 
ture of hydrochloric acid and potassic chlorate it is rapidly 
converted into tetrachlorquinone, (7 C C7 4 2 , a compound which 
is identical with chloranil, a product of the action of the same 
agents on carbolic acid, aniline, and other well-known bodies 
of the phenyl group. But although these reactions indicated a 
close relationship with the class of compounds formed around 
the carbon nucleus, represented in Fig. c, page 457, the first 
satisfactory theory in regard to the molecular structure of 
quinone was that advanced by Graebe in 1868. 1 lie concluded, 
as the result of a very extended investigation of the whole 
class of allied compounds, first, that the molecule of quinone 
contains the phenyl nucleus; secondly, that the two atoms of 
oxygen in this molecule are united together 
by a common bond, thus forming a dyad radi- , 

cal which aids in binding together two adja- ,, O % 

cent carbon atoms of the phenyl nucleus, thus : H~G GO 

so that, according to his view, quinone may jj-Q (j.q 

be regarded as derived from benzol by re- * Q ' 

placing two neighboring hydrogen atoms in ■ 

its molecules by the radical = [ 2 ]. 

1 Untersuchungen iiber die Chinongruppe, Ann. der Chem. und Pharm., 
CXLVI. 



5G0 QUINONE. [§ 496. 

The above conclusions are based chiefly on the following 
facts. In support of the first we have a large number of re- 
actions besides tho-e mentioned above, whose concurrent testi- 
mony leaves no doubt that the benzol and the quinone group 
of compounds are formed around the same carbon nucleus, so 
that if we accept Kekule's 1 theory in regard to the first, we 
must extend it also to the last. In support of the second, we 
have the fact that when by reactions, which are well under- 
stood, the oxygen of the quinone molecule is replaced by hy- 
dioxyl or chlorine, the two atoms are exchanged for only two 
atoms of these monad radicals, and not for four, as would be 
the case if the oxygen atoms were united to the carbon nucleus 
by all four of their bo ids. Thus, when quinone is acted on 
by hjdriodic acid it yields hydroquinone, whose symbol is 
CqH^Ho 2 , and oxid'zing agents change this body back to qui- 
none. Again, when tetrachlorquinone, (7 G CY 4 2 , is acted on 
by phosphoric chloride the products are C 6 Cl 6 and free chlorine 
gas. It is impossible, however, in a few words, to do justice to 
the arguments which Graebe advances in support of his theory, 
which will be found clearly stated in the paper already re- 
ferred to. 

In studying the derivatives of quinone Graebe recognized 
certain general characteristics, which he attributed to their 
supposed molecular structure. Of these, the most striking, 
after the two just illustrated, is the fact that two of the monad 
atoms, H or CI, associated with the oxygen radical, =[ 2 ~], in 
the molecular group may be readily replaced by Ho, H 2 N, or 
HS0 8 , the product being an acid, an amide, or a sulpho-acid. 
This well-marked character of the quinone group of compounds 
Graebe attributes to the influence of the atomic group [C 2 2 ] 
on the rest of the molecule, which, as he supposes, throws the 
neighboring atoms into a polar condition, similar to that pro- 
duced by CO in the organic acids and aldehydes. The three 
characteristics of the quinone group we have signalized are 
better illustrated by the chlorine derivatives of quinone than 
by quinone itself. Take, for example, tetrachlorquinone or 

1 Kekule" originated the theory in regard to the molecu'ar structure of the 
radical phenyl which has been presented in this book. For the evidence on 
which it is based we must refer to Kekule's well-known work on Organic 
Chemistry, as it is too extended to be given here ; also, Ann. Chem. und 
Pharm., CXXXVII. 129. 



§ 497.] NAPHTHOQUINONE. 561 

chloranil, mentioned above, which has the following chemical 
relations : — 

1. Reducing agents readily convert chloranil into tetrachlor- 
hydroquinone, C Q ClfHo 2 , a compound which oxidizing agents 
as readily change back to chloranil, and whose atoms of hydro- 
gen may be replaced by metals or organic radicals, giving such 
bodies as C Q Gl^Ko 2i O 6 0l 4 =-Eto 2 , C 6 Cl 4 =Aco 2 . 

2. When acted on by phosphoric chloride, chloranil yields 
C 6 Cl 6 and free chlorine, as stated above. 

3. If chloranil is dissolved in a solution of potassic hydrate, 
a metathesis takes place between Cl 2 in the first and Ko 2 in the 
last, in conformity with the third characteristic we have de- 
scribed, and if the proportions are rightly regulated there crys- 
tallize out from the solution red needles of potassic chloranil- 
ate, Ko.fC % Qlf[_0 2 ~\. From a solution of this salt hydrochloric 
or sulphuric acids precipitate chloranilic acid, Ho.f G 6 Cl 2 =[0 2 ~], 
in similarly colored crystals. 

Trichlorquinone, C 6 Ol 3 H0 2 , yields also similar derivatives, 
which for the most part contain C^Cl^Hm place of C§Cl 4 , but 
when treated with potassic hydrate it yields chloranilic acid, 
the same product which is obtained from tetrachlorquinone, 
showing that the single remaining hydrogen atom is one of the 
two replaced in the reaction. 

497. Naphtho-quinone. — Graebe's next step, in the course 
of investigation we are following, was to recognize in the com- 
pound we have called dichlordioxynaphthaline (495) a body 
having the same general structure as quinone. In a paper 
published in 1869, 1 he showed that this body, which he calls 
dichlornaphtho-quinone, 2 has the same general characteristics as 
tetra- or tri-chlorquinone. Thus it appears, 

1st. That dichlornaphtho-quinone, when acted on by reducing 
agents, yields dichlorhydronaphtho-quinone, 

C 10 ff 4 C'l 2 =\_O 2 '] + HH= C^U 4 Cl 2 -Ho 2 . 
Moreover, in this compound, as in tetrachlorhydro-quinone, 
Ho 2 may be replaced by Aco 2 . 

2d. That dichlornaphtho-quinone yields with phosphoric chlo- 
ride the compound C 10 Bs Ch, by which it is evident that, as in 

1 Ann. der Chem. und Pharm., CXLIX. 

2 The German name for quinone is chinon, and the names of the different 
quinone derivatives are formed from this root. 

24* J J 



562 ANTHRAQUINONE AND ALIZARINE. ' [§498. 

the ease of tetrachlorquinone, the group [0 2 ] is replaced by 
(7/ 2 , although at the same time a further replacement of the 
hydrogen atoms of the original naphthaline molecule is effected 
so that no free chlorine is evolved. 

3d. That when dichlornaphtho-quinone is dissolved in a solu- 
tion of potassic hydrate there are formed cherry-red needles 
of the potassic salt, of an acid corresponding to chloranilic 
acid, and from this salt, by the action of hydrochloric acid, the 
acid itself is readily obtained, as a yellow precipitate having 
the composition expressed by the symbol Ho- C 1(i H A Cb\_0^\. 
It will be noticed that in the reactions by which the so-called 
chloroxynaphthalic acid is formed only one atom of chlorine is 
replaced by hydroxyl, and not two, as in the case of chloranilic 
acid. The acid is a coloring matter, dyeing wool a scarlet or 
orange color, but has no affinity for alumina mordants. 

The above facts certainly justified the theory of Graebe 
in regard to the constitution of these derivatives of naphtha- 
line, and since his paper was published naphthoquinone itself, 
Cio ff(i = \_0-2], has been obtained. Thus the word "quinone" has' 
become the name of a class of compounds, and indicates the 
peculiar molecular structure we have described. 

Dichlornaphtho-quinone and chloroxynaphthalic acid were 
discovered by Laurent, 1836-40, and the great similarity, as 
indicated by ultimate analysis, between the last and alizarine 
was noticed soon after. Indeed, chloroxynaphthalic acid was 
for some time regarded as chlorinated alizarine, and this opin- 
ion was -apparently confirmed by the fact that both these sub- 
stances yield phthalic acid by decomposition with nitric acid. 
But about six years since Martius and Griess succeeded in 
replacing the single atom of chlorine in chloroxynaphthalic 
acid with hydrogen, and a coloring matter was obtained having 
the formula C 10 B G O s , which is identical with that assigned to 
alizarine by Strecker. This body, however, did not prove to 
be alizarine, although it was supposed at the time to be iso- 
meric with it. 

498. Anthraquinone and Alizarine. — Graebe, now associ- 
ated with Liebermann, beginning the investigation of alizarine 
at the point we left it in the last section, naturally inferred, 
from the resemblance to chloroxynaphthalic acid, that the col- 
oring matter of madder might be a similar acid, though derived 



§498.] ANTHRAQUINONE AND ALIZARINE. 563 

from a different qui none, and, in order to obtain some clew to 
the hydrocarbon to which it is related, these chemists sought 
as a first step to reduce natural alizarine by heating it with 
powdered zinc, adopting a method first suggested by Bayer for 
reducing similar compounds. The result was a solid body, 
which was soon recognized as identical with anthracene, a hy- 
drocarbon (C u ff l0 ) associated with naphthaline in coal-tar, and 
it was of course at once inferred that alizarine was the quinone 
acid of this well-known hydrocarbon, thus : — ■ 

C u ff w C u ff 8 2 Ho,=G lA H^0 2 \ 

Anthracene. Anthraquinone. Anthiaquinonic Acid or Alizarine. 

The formula of alizarine thus deduced, although differing from 
that of Strecker, agreed with that of Schunk, who had made 
a most extended investigation of the constituents of madder. 
Before, however, this theory of the constitution of alizarine 
could be established, it was essential to reverse the process of 
reduction and produce alizarine from anthracene, and the first 
step was to obtain the anthraquinone. Here again Graebe was 
aided by the previous investigations of Laurent, who long before 
had obtained an oxygenated derivative of anthracene, which he 
called, in accordance with a peculiar nomenclature of his own, 
anthracenuse. The substance had been re-examined by Ander- 
son, who gave it the symbol C u H 6 2 , and in it Graebe and Lie- 
bermann at once recognized the required quinone. It only 
now remained to replace two atoms of the hydrogen in this 
body by hydroxyl, in order to settle the question whether aliza- 
rine is the quinone acid of anthracene or not. The method 
was obvious. Anthraquinone was heated with bromine, which, 
replacing two of its hydrogen atoms, yielded the compound 
(7 14 i^#r 2 =[6y, and this heated to 180° with a solution of po- 
tassic hydrate gave an intense blue solution, from which hydro- 
chloric acid precipitated a yellow crystalline powder identical 
in every respect with the alizarine obtained from madder. 

This was the first instance of the artificial production of a 
vegetable coloring matter, and we have dwelt at more length 
than usual on the history of this beautiful discovery, because 
it affords an admirable illustration of the methods of modern 
chemistry. 1 Before the discovery could be applied in the arts 

1 la preparing this section we have been aided by an interesting paper of 
W. H. Perkins (Journal of Chem. Soc. of London, for 1870, page 133), in 
which specimens of points made with artificial alizarine are given. 



564 CONSTITUTION OF ANTHRACENE. [§500. 

it was of course essential that the synthetical process should 
be modified so as to adapt it to a manufacturing scale, and this 
has been in a great measure accomplished by substituting for 
bromine sulphuric acid, which when heated with anthraquinone 
converts it into a sulpho acid, {HS0 3 ).fG u H^\_0^ and this, 
like the corresponding bromine compound, yields alizarine when 
heated with potassic hydrate. 

499. Purpurine. — There is associated with alizarine in 
madder a second coloring material called purpurine, but as it 
is not absorbed by mordanted calicoes it has little commercial 
value. Like alizarine, it is reduced to anthracene by zinc 
powder, and the result of its ultimate analysis agrees very well 
with the symbol Ho^C u Hf[0.^\, but we have no further proof 
of its correctness. A third coloring principle has also been 
distinguished, called pseudopurpurine, whose analysis gave 
results corresponding to the symbol Ho^G^H^O^. It is 
probable that all three of these coloring materials occur in the 
madder-root as glucosides. 

500. Constitution of Anthracene. — We have now distin- 
guished three quinones, viz. benzoquinone, naphthoquinone, and 
anthraquinone. Graebe and Liebermann have shown in their 
recent paper 1 that the last has the chief characteristics we 
have distinguished in the other two, and that it gives simi- 
lar derivatives. It only remains to add a faw works in regard 
to its molecular constitution. In the paper just referred to 
Graebe and Liebermann advance the theory that the anthracene 
molecule has a structure which may be represented thus : — 

HO HO s 
HG V HO 
HG G , <7 N 
*Hd' * C ' HO 
HO + HO 
^HG 

Anthracene. 

and hence that anthracene bears the same relation to naphtha- 
line that naphthaline bears to benzol (428) and (495). This 
theory is not only rendered probable by the similar chemical 
relations of those three hydrocarbons which we have been 

i Ann. der Chem. und Pharm., VII. Supplementband, 1870, 312. 



§500.] CONSTITUTION OF ANTHRACENE. 565 

studying, but it also furnishes a satisfactory explanation of two 
synthetical processes by which anthracene has been produced. 

1. When benzylchloride, 6 H 5 - OH 2 - 01, is heated with water 
in a closed tube to 180°, anthracene is one of the chief pro- 
ducts. If we suppose that the production of the hydrocarbon 
results from the coalescing of two molecules of the chloride, 
the reaction may be indicated thus : — 

HO HO-H.Ol 
HO* % q' HOH,Ql 

HO ^ O 

'HO* V H H - o" " HO 

HO HO 

* ho' 

and it can readily be seen that if each molecule of the chloride 
gives up a molecule of HOI and an atom of H, we shall have 
the two halves of a molecule of anthracene as represented 
above. 

2. Anthracene may be also formed by passing a mixture of 
benzol and styrol (cinamene) vapors through a red-hot tube, 
and the same graphic symbol gives a very simple account of 
its production. 

HO HO^ 
HO* ^HO' *HC-H H 

i Styrol. „ i 

HO^ O „0 % 

^HO ' ^H H-o' HO 

, Benzol. M 

HO^ HO 
*HO' 

This synthesis was observed by Berthelot, who also obtained 
anthracene under similar conditions from toluol and also from 
a mixture of benzol and ethylene. Both processes admit of a 
similar simple explanation based on the above formula. In 
the last case the chief product is styrol, which probably pre- 
cedes the formation of anthracene. 

The three hydrocarbons, benzol, naphthaline, and anthra- 
cene, form a well-defined series, whose successive members 
differ from each other, not, as in the alcohol family, by CH& but 



566 CHRYSENE AND PYRENE. [§ 501. 

by C±H 2 , and to this corresponds a difference of about 140° in 
the boiling-points. 

CM Diff. G w ff 8 Diff. . G 14 ff 10 . 
B. P. 80° 136° 216° 144° 360° 

Apart from similar differences which the gradations in the 
series necessarily determine, these bodies strikingly resemble 
each other both in their physical and chemical qualities. The 
last point has been illustrated in this chapter so far as regards 
the formation of the quinone derivatives, and the impression 
produced by the facts here presented would be strengthened by 
a further study of the subject. All this of course indicates a 
similarity in the molecular structure of these bodies, and the 
cumulative evidence in favor of the theory here adopted is 
therefore much greater than that which can be obtained in re- 
gard to either of the substances separately. 

501. Ghrysene and Pyrene. — Since the identification of 
anthraquinone it has been discovered that two other hydrocar- 
bons associated with naphthaline and anthracene, among the 
least volatile of the products of the distillation of coal-tar, 
were capable of yielding derivatives belonging to the class of 
quinones. The names chrysene and pyrene were given by 
Laurent to impure products, and it is only very recently that 
these bodies have been isolated and their composition accu- 
rately determined. 1 Chrysene, G l8 H u . makes evidently the 
fourth term of the naphthaline series, differing from anthracene 
by G 4 H 2 , and its molecule may be CH-CH 

regarded as formed from that of 
anthracene by the addition of 
another phenyl nucleus, thus: 
Pyrene, C 16 /7J , although not be- 
longing to the same series, appears syrf 
to be similarly constituted, and 
may be regarded as phenylene- 
naphthaline (G 10 II ii Y(G 6 H 4 ). Chryso-quinone, Ci 8 H 10 [O 2 ~], has 
the chief characteristics of a true quinone, but in pyrene-qui- 
none, C m IT 8 [ 2 ], the characters are less strongly marked. 

1 Graebe und Liebermann, Ann. Chem. und Pharm., CLVIII., 285 and 299. 
June, 1871. 



GH 


GH 


0- 


G 


GHG 

r G- 


G-GH 
G GH 


C&CH 


CHrCH 



§ 502.] ELECTRICAL RELATIONS OF THE ATOMS. 567 



Electrical Measurements. 

502. Fundamental Laws. — The following formulas express 
the most important properties of electrical currents : — 

(1.) C=F^. (2.) G=J?. {3.)Q=Ct. (4.) W=C 2 Rt. (5.) W=QE. 

The first defines strength of current as a magnitude propor- 
tional to the force which it exerts on a magnetic pole under 
constant conditions. These conditions are the strength of pole, 
m, the length of the conductor, L, — assumed, as in the com- 
mon form of galvanometer, to be bent in a circle around the 
pole, — and the radius of this circle, K. The unit of force is 
that force which imparts to one gramme of matter the velocity 
of one metre in one second, and the unit pole that pole which 
at a distance of one metre repels a similar and equal pole with 
the unit force. 

The second is Ohm's formula (88), and expresses the prin- 
ciple, which can be readily demonstrated experimentally, that 
the strength of current, as defined by (1), is directly propor- 
tional to the electromotive force of the given circuit, and in- 
versely proportional to the resistance of the circuit. It also 
involves the still further truth that in different parts of the 
same circuit, where the strength of current is necessarily the 
same (88), the difference of tension or potential 1 between any 
two points is always proportional to the resistance between 
these points. 

The third expresses a truth first verified experimentally by 

1 The influence of the electromo ive force extends throughout the circuit, 
causiDg at every cross section of the conductor what we may call an electrical 
pressure, which regulates the flow of the electrical current. This pressure is 
greatest at the surface of the active plate where the power originates, and 
diminishes as we proceed round the circuit in either direction. At some 
intermediate section where the opposite currents neutralize each o'her the 
pressure is zero, and as Ave move back from this neutral point against the neg- 
ative current we encounter an ever-increasing "negative " pressure, while in 
the opposite direction we meet an ever-i creasing "positive" pressure. 
What we here call electrical pressure is called ebove tension or potential, and 
without attempting to give a theoretical conception of its nature, it is suffi- 
cient to say tha 1 : i". is a force measured at any point of the circuit by the ten- 
dency of the current to leave the conductor. Ohm's formula holds not only 
for the whole circuit, but also for any part of it; but in such cases E stands, 
not for the whole electromotive force, but for the difference of tension between 
the two ends of the portion under consideration. 



568 ELECTEICAL RELATIONS OF THE ATOMS. [§ 504. 

Faraday, that the quantity of electricity which passes any 
point of a circuit, as measured by the amount of electrolysis, 
is proportional to the strength of the current and the time dur- 
ing which it flows. 

The fourth expresses an important law, first demonstrated 
experimentally by Joule, that the work done by a current 
(e. g. the quantity of heat generated) is proportional to the 
square of the current, to the time during which it acts, and to 
the resistance which it encounters. It should be remembered 
in this connection that the unit of force acting through one 
metre does the unit of work ; that the force of gravity acting 
on one gramme of matter through one metre does 9.8 units of 
work, equal to one metre-gramme, and that the unit of heat 
(12) is equivalent to 4157.25 units of work or 423.8 metre- 
grammes. 

The fifth is involved in the previous three, from which it is 
readily deduced, and expresses the fact that the work done in 
any portion of the circuit is proportional to the quantity of 
electricity which passes over it and to the difference .of ten- 
sion between the two ends. 

503. Kirchhoff's Laws. — The following propositions may be 
deduced from the general theory of electrical currents : — 

1. The sum of the currents which approach any point is al- 
ways equal to those which recede from it. 

Or, if we distinguish the first by a plus and the second by a 
negative sign, we may say more generally : — 

The sum of all the currents which meet at a point is equal to 
zero. 

2. On any continuous line of conductors the sum of the pro- 
ducts of the resistances of the several parts by the strength of the 
current in each part is equal to the sum of the electromotive 
forces included in the same closed circuit. 

The last proposition holds true of every circuit which may 
be traced in any system of conductors and batteries, however 
complicated the maze ; only currents flowing in opposite direc- 
tions, with reference to the given circuit, must be distinguished 
by opposite signs. Moreover, the sum is equal to zero when 
there is no electromotive force on the line of conductors under 
consideration. 

504. Electrical Units. — In the following problems the val- 



§503.] ELECTRICAL RELATIONS OF THE ATOMS. 569 

lies C, R, or r and E of Ohm's formula are assumed to be 
measured in terms of the following units : First, the unit of 
current is that which would produce, by the electrolysis of wa- 
ter, 1 c. m. 3 of hydrogen and oxygen gas (measured under 
standard conditions) in one minute. Secondly, the unit of re- 
sistance is that offered by a pure silver or copper wire 1 m. 
long, and 1 m. m. in diameter at 0°. Lastly, the unit of elec- 
tromotive force is that which transmits a unit current against a 
unit resistance in a unit of time. 

By means of the magnetic and thermal relations given by 
(1) and (4) above, it is possible to express the values of the 
three elements of an electrical current in terms of the funda- 
mental units of space, weight and time, the metre, the gramme, 
and the second. The following formula? in which Z = length, 
M= mass or weight, and T '= time, are easily deduced, in- 
volving only simple mechanical principles : — 

Velocity = V= ~. 
Force = F = -jr = 
Work= W=FL = 
Work in metre-grammes 

Strength of pole 1 = m = 

Strength of current 2 = O 
Quantity of electricity 
Electro-motive force = 
Resistance = R = - = ~,= V. 

The values of C, R, and E, when the several factors in the for- 
mula? expressing their values are each taken equal to unity, 
are called the electromagnetic units. Thus the unit of resist- 

1 This value is readily obtained by considering that the force exerted 

_. mm 1 rrfi 

between the two poles must be Jt = -^ or = ^ 2 , when the two poles are 

equal. Hence, m = D\i~F. 

2 Readily derived from value of C, (1). 




For R the 


Ohm 


« 


U (f 


Megohm 


« 


u a 


Microhm 


« 


E " 


Volt 


<t 


u u 


Megavolt 


« 


a << 


Microvolt 


« 


C " 


Farad 


u 


" " 


Megafarad 
Microfarad 



570 ELECTRICAL RELATIONS OF THE ATOMS. [§504. 

ance is a velocity of one metre a second. 1 These absolute 
units, however, are of an order of magnitude which is unsuit- 
able for ordinary measurements, but the following very small 
multiples or submultiples may be used to advantage : — 

equal to 10? absolute units of resistance. 

" " 1013 " » " '• 

" « 10 " " " " 

" " 10 5 " " " electromotive force. 

« <( ion " " " " " 

" " 10-1 » u u u u 

" " 10 -8 " " " quantity per second. 

u « 10 _2 « (i u « 

u « 20 — 1-4 " " " " u " 

The unit current is a current of one Farad a second. 

A pure copper or silver wire 1 m. m. in diameter and 48.61 
metres long has a resistance of one Ohm at 65° F., and the 
Committee of the British Association on Electrical Standards 
have carefully constructed a standard Ohm of which copies are 
readily accessible. Further, we have a closely approximate 
standard of electromotive force in the Daniell's cell, which* ac- 
cording to Sir W. Thompson, is equal to 1.079 Volts, or 1 
Volt = 0.9268 of force of Daniell's cell. One Volt equals 
about 500.6 of the old units, and a current of one Megafarad 
per second will yield during one minute by the electrolysis of 
water 10.3 c. m. 3 of gas very nearly. 

The admirable instruments now constructed for the purpose 
enable us to use the B. A. units, as they are called, with great 
facility, but in solving the following problems the older system 
will be found more convenient. The student, however, should 
familiarize himself with both ; but he should bear in mind that 
values in Ohm's Volts and Farads must be reduced to absolute 
units before they can be substituted for C, R, or E in Ohm's 
formula. 

Questions and Problems. 

1. What resistance does the current suffer in an iron wire 50 me- 
tres long and 5 m. m. diameter ? Sp. R. of iron 7. 

Ans. 14 units. 

2. Assuming that the Sp. R. of copper is 1.3 and that of iron 7, 
what must be the diameter of an iron wire which will oppose no 
greater resistance to the current than a copper wire of 2 m.m. diam- 
eter? Ans. 4.64 m. m. 

1 For the interpre f ation of this remarkable analytical result see pamphlet 
by the author on Absolute System of Electrical Measurements. 



ELECTEICAL RELATIONS OF THE ATOMS. 571 

3. It is found by experiment that a wire of German silver, 7.201 
m. long and 1.5 m. m. diameter, opposes the same resistance to the 
current as a wire of pure silver 10 m. long and ^ m. m. diameter. 
What is the Sp. R. of German silver. Ans. 12.5. 

4. It is required to make with 132.8 grammes of pure silver, a 
wire which will offer a resistance of 81 units. What must be its 
length and diameter ? Sp. Gr. of silver = 10.57. 

Solution. Representing by x the length in metres, and by y the 

diameter in millimetres, we deduce by [1] y 1 x — 10.57 = 132.8 and 
by the laws of conduction -j = 81. Whence x — 36 m. and y = 
f m. m. 

5. What is the length and diameter of an iron wire weighing 
97.38 grammes, which offers a resistance of 9,072 units ? It is known 
that the Sp. Gr. of the iron = 7.75 and its Sp. R. = 7. 

Ans. Length, 144 m. Diameter, \ m. m. 

6. From a given wire there are four branches, of which the re- 
sistance is respectively 10, 20, 30, and 40. Required the total 
resistance when the current passes simultaneously through the four 
branches. 

Solution. The resistance in the first branch may be represented 
by a normal silver wire 10 m. long and 1 m. m. diameter. If we 
call the area of a transverse section of this wire s, then the resist- 
ance in the other three branches will be represented by normal wires 
of the same length, but having on the cross sections the areas 1 s, 
\s and is respectively. If next we conceive of these wires as 
merged in one, having the common length 10 m. and an area on the 
section equal to (1 -f \ -j- \ -f- J) s, it is evident that such a wire 
will represent the resistance required. Hence we easily deduce, 

Ans. 4.8. 

7. A closed circuit has two branches through which the current 
passes simultaneously. In one branch r = 100. What length of 
copper wire 5 m. m. diameter must be used for the other that the 
total r == 50 ? Ans. 2.500 metres. 

8. A conductor has two branches, one having r = 756, the other 
so adjusted that when the current passes at the same time through 
both, the total resistance equals 540. Required the length of a Ger- 
man silver wire \ m. m. diameter and Sp. R. = 12.5, which, when 
inserted in the adjusted branch, will increase the total resistance to 630. 

Solution. By principle of last problem we easily find that the 
resistance in the adjusted branch before insertion equals 1,890, and 
after insertion, 3,780. The difference between these values, 1,890, 
is the resistance due to the inserted wire. Hence its length must be 
37.8 metres. 



572 ELECTRICAL RELATIONS OF THE ATOMS. 

9. We have a battery of six Daniells cells, in each of which 
12=475, R = 15, and the external resistance against which the 
battery is to work, r = 10. The cells may be arranged, 1st, as six 
single elements ; 2d, as three double elements ; x 3d, as two threes-fold 
elements ; 4th, as one six-fold element. Required the current strength 
in each case. Ans. 28.5, 43.8, 47.5 and 38.0 respectively. 

10. We have a battery of twelve Grove cells, in each of which 
E = 830, and R =18, to work against an external resistance of 
r = 24. Required the strength of current when the cells are ar- 
ranged, 1st, as twelve single; 2d, as six two-fold ; 3d, as four three- 
fold; 4th, as three four-fold; 5th, as two six-fold, and 6th, as one 
twelve-lold element. 

Ans. 41.5, 63.8, 69.2, 66.4, 55.3, and 32.5 respectively. 

11. With a single cell, where E and R have a constant value, 
what is the maximum strength of current, and under what condi- 
tions would it be obtained ? 

Ans. -n, when the external resistance is nothing. 

12. With n cells in each of which E and R have the same value, 
what is the maximum strength of current, and under what condi- 
tions would it be obtained ? 

Ans. n p , when the cells are arranged as one n-fold element, 
and work against no external resistance. 

13. With n cells as above, working against a given external resist- 
ance r, how should they be arranged so as to obtain the maximum 
value of C ? 

Ans. So as to make the internal resistance equal to that of the 
external circuit. 

Solution. If x represents the number of compound elements formed 
with the n cells when C in Ohm's formula is a maximum, we should 
evidently have under this condition x compound elements, each 

formed of - cells. The electromotive force of such an arrangement 

would be x E. The internal resistance would be x R — — = — R 

' x n 

(compare problems 8 and 9), and the strength of the maximum 
current required, 

-R4-r 

n ' 

* By double elements is meant a group of two cells coupled for quantity 
(§ 89) and equivalent to a large cell having plates of twice the size. Six 
double elements are six such groups arranged for intensity, and the other 
terms have a similar meaning. 



ELECTRICAL RELATIONS OF THE ATOMS. 573 

The first differential coefficient of this function of x when C is a 
maximum must be equal to zero. Hence, 



S*+0 



2- RE 



£*+■') 



= 



or r = - JR. 

n 

That is, the strength of the current is at its maximum when the in- 
ternal equals the external resistance, as stated above. Those who 
are not familiar with the elementary principles of the differential 
calculus may satisfy themselves of the truth of this result by com- 
paring the answers obtained to problems 8 and 9. 

14. We have, in the first place, for a single cell of a given combi- 
nation working against a feeble resistance, the value C = ff ; 
in the second place, for n cells of the same combination working 

against n times the resistance, the identical value C — „ , . In 

& nR + nr 

" strength " the two currents are equal, but are they identical ? 

15. In a given cell E = 475 ; R = 15. The current passes 
through 30 metres pure copper wire 2 m. m. diameter. It is re- 
quired to arrange 8 cells so that C may be the greatest possible. 

Ans. They should be arranged as two four-fold elements. 

16. We have a battery of four Bunsen cells (E = 800, R = 4 
each), coupled as four single elements. The circuit is closed through 
500 grammes of pure copper wire. Required the greatest strength 
of current, and the dimensions of the wire that this maximum may 
be obtained. 

17. A simple Voltaic cell, whose electromotive force E is known, 
working against an unknown total resistance K (both external and 
internal), produces a given effect upon a galvanometer. Another 
cell differently constructed, working against a total resistance R'\ 
also unknown, produces the same effect upon the galvanometer. It 
is also observed that a measured length I of normal copper wire, in- 
serted in the first circuit, produces on the galvanometer the same 
difference of effect as a length V inserted in the second circuit. 
Required the electromotive force E' of the second cell. 

Solution. We easily deduce from Ohm's formula the two equations 

| = fz and j^p = J^- p whence we obtain, - 

Ans. E' = E l j. 



574 ELECTEICAL RELATIONS OF THE ATOMS. 

18. In order to determine the electromotive force of a Bunsen's 
cell, it was compared, as in last problem, with a Daniell's cell whose 
electromotive force was known to be 470. After adjusting the ex- 
ternal resistances so that both produced the same effect upon the 
galvanometer, it was found that the insertion of 5.6 m. of copper 
wire into the first circuit caused the same change in the instrument 
asthe insertion of 3.29 metres of the same wire in the circuit of the 
Daniells cell. What was the electromotive force sought ? 

Ans. 800. 

19. A battery of 40 Bunsen's cells remains closed for an hour, and 
during that time furnishes a current who.se strength C — 30. How 
much zinc will be consumed in this time, assuming that there is 
no local action ? 

Solution. Such a current would produce, by the electrolysis of 
water, 30 cTm. 3 of gas in one minute, or 1.8 litres in one hour. Of 
this gas 1.2 litres or 1.2 criths would be hydrogen. The chemical 
equivalent of zinc being 32.6, the amount of zinc dissolved in each 
cell must be 1.2 X 32.6 =± 39.12 criths, and in the forty cells 
1564.8 criths, equal to 140 grammes, the answer required. 

20. In an electrotype apparatus, Fig. 85, 16.36 grammes of cop- 
per were deposited on the negative mould in 24 hours. What was 
the strength of current ? Ans. 6 units. 

21. In an electrotype apparatus the electromotive force of the 
single cell employed is 420, and the internal resistance 5. The ex- 
ternal resistance, including decomposing cell, is 0.25. How much 
copper will bd deposited on the negative mould in one hour, and 
how much zinc will be dissolved in the battery during the same 
time ? Ans. 9.088 grammes copper and 9.346 grammes of zinc. 

22. Thirty-two Grove cells (E = 830, R = 20 each) are con- 
nected as 4 eight-fold compound elements and the current employed 
to work an electro-silvering apparatus, in which the total resistance 
external to the battery was equivalent to 10. Required the number 
of grammes of silver deposited each hour, an 1 the number of grammes 
of zinc dissolved during the same time in the battery. 

Ans. 64.24 grammes of silver and 7 7.56 grammes of zinc. 

23. Assuming that the external resistance cannot be changed, 
could the same number of cells of the battery described in last 
problem be so arranged as to deposit more silver in the same time ? 

Ans. They could not. 
Could they be so arranged as to deposit the same amount of silver 
with less expense of zinc ? What would be the most economical ar- 
rangement, and under these conditions how much silver would be 
deposited in one hour and how much zinc dissolved ? 

Answer to last question, 30.25 grammes silver, and 9.13 grammes 
of zinc. 



ELECTRICAL RELATIONS OF THE ATOMS. 



575 



24. What is the current through 25 Ohm with a tension of 5 

Volts ? 

P 5 X 10 3 

Ans. C= T = — = 0.5 X 10- 2 or 0.5 Megafarad. 

R 25 X 10 7 ° 

25. What is the work done by a current of 5 Megafarads per sec- 
ond through a resistance of 10 Ohms? 

Ans. W = C.Jit = (5 X 10~ 2 ) 2 X 10 X 10 7 = 250,000 units 
per second. 

26. What is the work done by one thousand Farads in falling in 
tension one Volt ? 

Ans. W= QE == 1000 X 10~ 8 X 10 5 = 1000 X 10" 3 = 1 unit 
of work. Hence, 9,800 Voltfarads equal one metregrainme. 

27. What would be the answers to Problem 10 in B. A. units? 
Assuming that nine tenths of the external resistance is in a coil of 
platinum wire surrounded by a kilogramme of water, how high 
would the temperature of the water be raised in ten minutes ? 

28. Assuming that in the system 
of conductors represented in Fig. 3, 
E represents the electromotive force 
of the voltaic element, it the total 
resistance of the main conductor a E 
h, R t and R 2 the resistances of the 
two conductors into which the main 
stream divides, find the values of the 

three corresponding currents C, C v and C 2 in terms of E, R, R v 
and R r 




Prove also that C, : C„ 



C: 



n-2 



Rt 



« *. = ** + * 



: R 2 : R v and further, that 
Lastly, show that the equiva- 



Cl " ~R l + R 2 

lent resistance of any number of branches may be found by adding 
together the reciprocals of each branch and taking the reciprocal of 
this sum. A conductor like i? 2 , 
which diverts a portion of the main 
current, from R v is called a shunt, 
and if R 1 h the coil of a galva- 
nometer the galvanometer would 
be said to be shunted by R 2 , and 
by adjusting the value of R 2 to R t 
we can cause a known fraction of 
the whole current to pass through 
the instrument. 

29. In the system of conductors represented in Fig. 4, called 
Wheatstone's bridge, no current passes over the bridge between c 



: : Cr 


*J\H*- ' 


^ 









and d when R, 



^2 = ^3 : -^4* 



Prove the truth of this proposition, 



576 



ELECTKICAL EELATIONS OF THE ATOMS. 



and show how it may be applied for measuring resistances when 

we have a set of standard resistance 
coils. 



jV/'P" 



30. In the system of conductors, 
represented in Fig. 5, prove that no 
current passes in the portion a E 1 b 
£i R 



when — = 



and consider 



e ' r + r; 

how the system may be used for 
comparing the electromotive force 
of different cells. 



TABLE I. 

FRENCH MEASURES 

Measures of Length. 



1 Kilometre = 

1 Hectometre = 

1 Decametre = 

1 Metre = 



1000 Metres. 
100 
10 
1 



1 Metre 
1 Decimetre 
1 Centimetre 
1 Millimetre 



1.000 Metre. 
0.100 " 
0.010 " 
0.001 " 



Logarithms. 
9.7933 712 



Ar. Co. Log. 
0.2066 188 



1 Kilometre = 0.6214 Mile. 

1 Metre = 3.2809 Feet. 0.5159 930 9.4840 070 

1 Centimetre = 0.3937 Inch. 9.5951 742 0.4048 258 

The metre is one ten-millionth of a quadrant of the globe. 



Measures of Volume. 

1 Cubic Metre nT 3 = 1000.000 Litres. 

1 Cubic Decimetre dTTri. 3 = 1.000 " 

1 Cubic Centimetre cTln. 3 = 0.001 " 



Logarithms. Ar. Co. Log. 

1 Cubic Metre = 35.31660 Cubic Feet. 1.5479 790 8.4520 210 

1 Cubic Decimetre = 61.02709 Cubic Inches. 1.7855 226 8.2144 774 

1 Cubic Centimetre = 0.06103 " " 8.7855 226 1.2144 774 

1 Litre = 0.22017 Gallon. 9.3427 581 0.6572 419 

1 Litre = 0.88066 Quart. 9.9448 083 0.0551 917 

1 Litre = 1.76133 Pints. 0.2458 407 9.7541593 



FRENCH 

1 Kilogramme = 1000 Grammes. 
1 Hectogramme =100 " 

1 Decagramme =10 " 

1 Gramme = I " 



WEIGHTS. 

1 Gramme =1.000 Gramme. 

1 Decigramme =0.100 " 
1 Centigramme =0.010 " 
1 Milligramme =0.001 " 



Logarithms. Ar. Co. Log. 

1 Kilogramme = 2.20462 Pounds Avoirdupois. 0.3433 337 9.6566 663 

1 " = 2.67922 " Troy. 0.4280 083 9.5719 917 

1 Gramme = 15.43235 Grains. 1.1884 321 8.8115 679 



1 Crith 



= 0.089578 Grammes. 



8.9522 014 1.0477 986 



TABLE II. 



ELEMENTARY ATOMS. 



Perissad 
Elements. 


If 


« 8 




Artiad 
Elements. 


11 


>> o 


i • 

a a 

rjr-1 

<3 

— ir~ 
<< 

(< 

it 

it 
a 

tt 

n 
a 

tt 
tt 
it 

II or IV 

(< 

tt 

tt 
a 
it 

tc 
tt 
It 
ti 

IV 


Hydrogen 

Fluorine 

Chlorine 

Bromine 

Iodine 


1.0 

19.0 

35.5 

800 

127.0 

7.0 

230 

39.1 

85.4 

133.0 

108.0 

204.0 

197.0 

11.0 

140 

31.0 

75.0 

122.0 


H-H 
F-F 

CI- CI 

Br- Br 

l-l 

Li-Li 
Na-Xa 

K-K 
Rb-Rb 

Cs- Cs 
Ag-Ag ? 
fl-Tl? 
AmAu? 

B-=B? 

N=N 

AsgA*, 

SblSbJ 


I 

tt 
a 
a 

a 

tt 
it 
tt 
ic 

I or III 
III 

III or V 

a 
tt 

a 
n 
a 

V 

It 


Copper 
Mercury 


63.4 

200.0 

40.0 

87 6 

137.0 

207.0 

24.0 

65.2 

72.0 

112.0 

9.3 

61.7 

112.6 

92.0 

93.6 

95.0 

58 8 

58.8 

55.0 

56.0 

52.2 

27.4 

104.4 

199.2 

104.4 

196.0 

106.6 

197.4 

50.0 

1180 

89.6 

231.4 

28.0 

12.0 


Cu? 
Hg 

Ca? 
Srt 
Ba? 
Pb? 
Ma? 
Zn? 

In? 

Cd 

G? 

Y? 

E? 

Ce? 

La? 

D? 
Ni? 

Co? 
Mr, ? 
Fe? 
Cr? 
Al? 
Ru ? 
Os? 
Rh 
lr? 
Pd? 
Ft? 
Ti? 
Sn? 
Zr? 
Th? 
Si? 
C? 


Calcium 
Strontium 
Barium 
Lead 


Lithium 

Sodium 

Potassium 

Rubidium 

Caesium 


Magnesium 
Zinc 


Indium 
Cadmium 


Silver 


Glucinum 

Yttrium 

Erbium 


Thallium 
Gold - 


Boron 


Cerium 

Lanthanum 

Didymium 


Nitrogen 

Phosphorus 

Arsenic 

Antimony 

Bismuth 


Nickel 
Cobalt 


210.0 \Bi^Bi. 2 ? 


Manganese 
Iron 


Vanadium 


51.37 
120.0 


v-=v? 

U=U? 


Uranium 


Chromium 
Aluminum 


Columbium 
Tantalum 


94.0 Cb^Cb? 
\82.0\TaiTa? 


Ruthenium 
Osmium 


Artiad 
Elements. 


16.0 

32.0 

79.4 

128.C 


0-0 

S--S 
Se--Se 
Te=Te 


II 

II or VI 
it 

t< 

VI 

1 " 


Rhodium 
\lridium 


Palladium 
Platinum 


Titanium 
Tin 


Oxygen 


Sulphur 
Selenium 
Tellurium 


\Zirconium 
| Thorium 


96 Mn ? 


^ilicon 


Moli/bdenum 
Tungsten 


184.C 


! w? 


! Carbon 



TABLE III. 



Specific Gravity of Gases and Vapors. 



m 



Names. 


Symbols. 


Sp.ffir. 


Sp.Gr. 


Half 

Molecular 


Loga- 

ri til ms 






Air = 1. 

L00(T 


H-H=\. 
14.43 


Weight 




Air 




11593 


Hydrogen 


H-H 


0.0693 


1.00 


1.00 


0.0000 


Acetylic Hydride (Aldehyde) 


C 2 H 3 0-H 


1.532 


22.10 


22.C0 


1.3424 


Acetylic Chloride 


c 2 H^o-a 


2.87 


41.42 


39.25 


1.5938 


Acetic Anhydride 


(C 2 H 3 0) 2 =0 


347 


50.07 


51.00 


1.7076 


Acetic Acid 


H-0-C 2 H 3 


2.083 


30.07 


30.C0 


1.4771 


Alumiuic Chloride 


umci 6 


9.34 


134.80 


133.99 


2.1268 


Alumiuic Bromide 


uyfa-e 


18.62 


268.70 


267.40 


2.4272 


Aluniinic Iodide 


[Al 2 ]=£ a 


27. 


389.60 


4C8.40 


2.6111 


Antimonious Chloride 


sb=a 3 


7.8 


112.70 


114.20 


2.0577 


Triethylstibine 


(C 2 H 5 ) 3 =Sb 


7.23 


104.40 


104X0 


2.0191 


Arsenic 


As 2 =As 2 


10.6 


153.00 


150.00 


2.1761 


Arseniuretted Hydrogen 


H 3 =As 


2.695 


38.90 


39.C0 


1.5911 


Triethylarsine 


(C 2 H-,) 3 ^As 


5.29 


76.35 


81.C0 


1.9085 


Kakodyl 


( CH 3 ) 2 As-( CH 3 ) 2 As 


7.10 


102.50 


105.C0 


2.0212 


Arsenious Chloride 


As = Cl 3 


6.3 


90.90 


90.75 


19578 


Arsenious Iodide 


As=I 3 


16.1 


232.40 


228.00 


2.3579 


Bismuthous Chloride 


Bi = Cl 3 


11.35 


163.90 


158.25 


2.1994 


Boric Methide 


(CH 3 ) 3 =B 


1.931 


27.90 


28.00 


1.4472 


Boric Ethide 


(C 2 H 5 ) 3 =JB 


3.4C1 


49.10 


49.00 


1.6902 


Boric Fluoride 


B=F S 


2.37 


34.20 


34.00 


1.5315 


Boric Chloride 


B=Cl 3 


3 942 


56.85 


58.75 


1.7690 


Boric Bromide 


B=Br 3 


8.78 


126.80 


12550 


2.0986 


Methylic Borate 


(CH 3 ) 3 = 3 =B 


3.59 


51.80 


52.00 


1.7160 


E thy lie Borate 


(C 2 H 5 ) 3 =0 3 =B 


5.14 


74.20 


73.00 


1.8633 


Bromine 


B>-Br 


5.54 


79.50 


80.00 


1.9C31 


Hydrobromic Acid 


H-Br 


2.71 


39.10 


40.50 


1.6075 


Carbonic Tetrachloride 


Clf? 4 


5.415 


78.14 


77.00 


1.8865 


Marsh Gas 


CH 4 


0.5576 


8.05 


8.00 


0.9031 


Phosgene Gas 


C*iO, Cl 2 


3.399 


49.06 


49.50 


1.6946 


Dicarbonic Hexachloride 


[C-C]%Cl & 


8.157 


117.70 


118.50 


2.0737 


Dicarbonic Tetrachloride 


[c=q=a 4 


5.82 


84.00 


83.00 


1.9191 


Dicarbonic Dichloride 


[C=C] = Cl 2 






47.50 


1.67G7 


Carbonic Oxide 


c=o 


0.967 


13.95 


14.C0 


1.1481 


Carbonic Anhydride 


c=o 2 


1.529 


2206 


22.00 


13424 


Carbonic Sulphide 


c=s 2 


2.645 


38.17 


38.00 


1.5798 


Chlorine 


Cl-Cl 


2.44 


35.22 


35.50 


1.5502 


Hydrochloric Acid 


H-Cl 


1.27 


1832 


18.25 


1.2613 


Chromic Oxychloride 


Cte0 2 , Cl 2 


5.5 


79.40 


77.6 


1.8935 


Columbic Chloride 


CbgCl 5 


9.6 


138.60 


135.70 


2.1326 


Columbic Oxychloride 


Cb = 0,Cl 3 


7.9 


114.00 


108.20 


2X342 


Cyanogen 


CN-CN 


1.806 


26.06 


26.00 


1.4150 


Hydrocyanic Acid 


H-CN 


0.947 


13.67 


13.50 


1.1S03 


Ethyl 


Co /I- - C9 -".5 


2.0 


28.86 


29.00 


1.4624 


Ethylic Chloride 


(hHr,)-Cl 


2.219 


32.02 


32.25 


1.5085 


Ethylic Oxide (Ether) 


(cIh^o 


2.586 


37.32 


37.00 


1.5682 


Ethylic Hydrate (Alcohol) 


C 2 Hr-0-H 


1.613 


23.28 


23.00 


13317 



TABLE III. (Continued.) 



Names. 


Symbols. 


Sp.ffir. Sp.Gr. 


Half 

Molecular 


Loga- 
rithms. 






Ajr =^1 


H-H=\. 


Weight. ] 


Ethylene (Olefiant Gas) 


C,H 4 


0.978 


14.11 


14.00 


1.1461 


" Chloride (Dutch Liq.) 


(C.H^Cl^ 


3.443 


49.69 


49 50 


1.6946 


Ethylene Oxide 


(C 2 H 4 ) = 


1.422 


20.52 


22.00 


1.3424 


Ethylene Hydrate (Glycol) 


(C 2 H^0 2 =H 2 






31.00 


1.4914 


Ferric Chloride 


[Fe 2 ]lCl 6 


11.39 


164.40 


162.50 


2.2108 


Iodine 


I-I 


8.716 


125.90 


127.00 


2.1038 


Hydriodic Acid 


H-I 


4.443 


64.12 


64.00 


1.8062 


Mercury j 


Hg 


6.976 


100 70 


10000 


2.0000 


Mercuric Ethide 


(C 2 H,) 2 =Hg 


9.97 


143.90 


129.00 


2.1106 


Mercuric Methide 


(CH 3 ) 2 =Hg 


8.29 


119.60 


115.00 


2.0607 


Mercuric Chloride 


Hg = Cl 2 


9.8 


141.50 


135.50 


2.1319 


Mercuric Bromide 


Hg=Br 2 


12.16 


175.60 


180.00 


2.2553 


Mercuric Iodide 


Hg=I 2 


15.9 


229.60 


227.00 


2.3560 


Mercurous Chloride 


[Hg 2 ] = Cl 2 


8.21 


118.50 


23550 


2.3720 


Nitrogen 


N=N 


0.971 


14.00 


14.00 


1.1461 


Ammonia 


H^N 


0.591 


8.535 


8.51 


0.9294 


Methylamine 


H 2 ,(CH 3 )=N 


1.08 


15.59 


15.50 


1.1903 


Aniline 


H 2 ,(C G H 5 )=N . 


3.21 


46.33 


46.50 


1.6675 


Nitrous Oxide 


N 2 


1.527 


22.04 


22.00 


1.3424 


Nitric Oxide 


NO 


1.038 


14.97 


15 00 


1.1761 


Nitric Peroxide 


N0 2 


1.72 


24.82 


23.00 


1.3617 


Osmic Tetroxide 


OsO t 


8.89 


128.30 


131.60 


2.1193 


Oxygen 


= 


1.1056 


15.95 


16.00 


1.2041 


Aqueous Vapor 


H 2 = 


0.6235 


8.998 " 


9.00 


0.9542 


Phosphorus 


P^P 2 


4.42 


63.78 


62.00 


1.7924 


Phosphuretted Hydrogen 


H 3 =P 


1.184 


17.09 


17.00 


1.2304 


Phosphorous Chloride 


P=Cl 3 


4.742 


68.44 


68.75 


1.8373 


Phosphoric Oxychloride 


PIO, Cl 3 


5.3 


76.49 


76.75 


1.8851 


Oxide of Triethylphosphine 


((C 2 H 5 ) 3 =P) = 


4.6 


66.39 


67.00 


1.8261 


Selenium, at 771° 


Se=Se 


5.68 


81.96 


79.40 


1.8998 


Seleniuretted Hydrogen 


H 2 = Se 


2.795 


40.33 


40.70 


1.6096 


Silicic Methide 


(CH 3 \m 


3.083 


44.49 


44.00 


1.6435 


Silicic Ethide 


(C 2 H 5 ) i= Si 


5.13 


74.03 


72.00 


1.8573 


Silicic Fluoride 


Si=F t 


3.600 


51.95 


52 00 


1.7160 


Silicic Chloride 


Si^Cli 


5.939 


85.72 


85.00 


1.9294 


Ethylic Silicate 


(C 2 ff 5 ) 4 = 4 iSi 


7.32 


105.60 


104.00 


1.0170 


Stannic Ethide 


(C 2 H 5 )^Sn_ 


8.021 


115.80 


117.00 


2.0682 


Stannic Dimethylo-diethide 


( CH 3 ) 2 , ( C 2 H 5 ) 2 =Sn 


6.838 


98.68 


103.00 


2.0128 


Stannic Chloro-triethide 


a, ( C 2 HJ 3 =Sn 


8.430 


121.70 


120.20 


2.0799 


Stannic Dichloro-diethide 


Cl 2 , ( C 2 HJ 2 =Sn 


8.710 


125.70 


123.50 


2.0917 


Stannic Chloride. 


Sn^Cli 


9.199 


132.70 


130.00 


2.1139 


Sulphur above 86CP 


S=S 


2.23 


32.18 


32.00 


15051 


Sulphur at 450° 


^ 


6.617 


95.50 


98.00 


1.9823 


Sulphuretted Hydrogen 


H„=S 


1.191 


17.19 


17.00 


1.2304 


Sulphurous Anhydride 


S=0 2 


2.234 


32.24 


32.00 


1.5051 


Sulphuric Anhydride 


SiO s 


2.763 


39.87 


40.00 


1.6021 


Tantalic Chloride 


TaCl 5 


12.8 


184.70 


179.70 


2.2546 


Titanic Chloride 


TiClt 


6.836 


98.65 


96.00 


1.9823 


Zinc Ethide 


(C 2 H 5 ) 2 =Zn 


4.259 


61.46 


61.60 


1.7896 


Zirc Chloride 


?-fn. 


8.15 


117.60 


11 K §0 


10637 



LOGARITHMS AND ANTILOGARITIIMS. 



LOGARITHMS OF NUMBERS. 


2 ¥ 

z 25 





1 


2 

0086 


3 


4 


5 

0212 


6 

0253 


7 

0294 


8 

0334 


9 

0374 


Proportional Parts. 


1 

4 


2 

8 


3 
12 


4 5 

17 21 


6 7|8 


9 


10 


0000 


0043 


01280170 


25 29 33 37 


11J0414J0453 


0492 


0531 0569 


0607 


0645 0682 


0719 


0755 


4 


8 


ii 


15 L 19 


23 26 30 34 


12 0792 0828 


0864 


0899 0934 


0969 


1004 


1038 


1072 


1106 


3 


7 


10 


14*17 


21 24 28 ' 31 


13 1139 1173 


1206 


1239 1271 


1303 


1335 


1367 


1399 


1430 


3 


6 


10 


13 f 16 


19 23 1 26 29 


14 


1461,1492 


1523 


1553' 1584 


1614 


1644 


1673 


1703 


1732 


3 


6 


9 


12* 15 
I 


18 21 24 27 


15 


1761 1790 


1818 


1847 1875 


1903 


1931 


1959 


1987 


2014 


3 


6 


8 


11 14 


17 20 22 25 


16 


2041 2068 


2095 


21222148 


2175 


2201 


2227 


2253 


2279 


3 


5 


8 


11 s 13 


16 IS' 21 24 


17 


230412330 


2355 


2380 2405 


2430 


2455 


2480 


2504 


2529 


2 


5 


7 


10,12 


15 17| 20 22 


18 -2553 -2577 


2601 


2625 2648 


2672 


2695 


2718 


2742 


2765 


2 


5 


7 


9 12 


14 16 19 21 


19 


2788! 28 iO 


2833 


2856 2878 


2900 


2923 


2945 


2967 


2989 


2 


4 


7 


911 
■ 


13 16 18 

1 | 


20 


20 


3010.3032 


3054 


3075 3096 


3118 


3139 3160 


3181 


3201 


a 


4 


6 


61, 


1 
13 15 17 


19 


21 


3222 3243 


3263 


3284 3304 


3324 


3345 3365 


3385 


3404 


2 


4 


6 


8 10 


12 14 16 


I 18 


22 


3424 3444 


3464 


3483 3502 


3522 


3541 


3560 


3579 


3598 


2 


4 


6 


8*10 


12 14' 15 


17 


23 


3617 3636 


3655 


3674 3692 


3711 


3729 


3747 


3766 


3784 


2 


4 


6 


7 


9 


ll' 13 15 


17 


24 


3802 3820 


3838 


3856 3874 


3892 


3909 


3927 


3945 


3962 


2 


4 


5 


7 


9 


11 12 14 


16 


25 


3979 3997 


1014 


4031 


4048 


4065 


4082 


4099 


4116 


4133 


2 


3 


5 


7 


9 


10, 12 14 


15 


26 


4150,4166 


4183 


4200 


4216 


4232 


4249 


4265 


4281 


4298 


2 


3 


5 


7 


S 


10 11 13 


15 


27 


4314 


4330 


4346 


4362 


4378 


4393 


4409 


4425 


4440 


4456 


2 


3 


5 


6 


6 


9 11 13 


14 


28 


4472 


4487 


4502 


4518 4533 


4548 


4564 


4579 


4594 


46C9 


2 


3 


5 


6 


8 


9 11 12 


14 


29 


4624 


4639 


4654 


4669 


4683 


4698 


4713 


4728 


4742 


4757 


1 


3 


4 


6 


7 


9 


10 12 

| 


13 


30 


4771 


4786 


-1800 


4814 


4829 


4843 


4857 


4871 


4886 


4900 


i 


3 


4 6 


7 


9 


10 11 


13 


31 


4914 


4928 


4942 


4955 


4969 


4983 


4997 


5011 


5024 


5038 


1 


3 


4 6 


7 


8 


10 11 


12 


32 


5051 50655079 


5092 


5105 


5119 


5132 


5145 


5159 


5172 


1 


3 


4 5 


7 


8 


9 11 


12 


33 


5185J5198 5211 


5224 


5237 


5250 


5263 5276 


5289 


5302 


1 


3 


4 5 


6 


8 


9 10 


12 


34 


5315 


5328 5340 


5353 


5366 


5378 


5391 .5403 


5416 


5428 


1 


3 


4 5 

| 


6 


8 


9 10 


11 


35 


5441 


5453 5465 


5478 


5490 


5502 


5514 5527 


5539 


5551 


1 


2 


*'« 


6 


7 


9 10 


11 


36 


5563 5575 5587 


5599 5611 


5623 


5635,5647 


5658 


5670 


1 


2 


4 5 


6 


7 


8 


10 


» 


37 


5682 5694 


5705 


5717 


5729 


5740 


5752 5763 


5775 


5786 


1 


2 


3 5 


6 


7 


8 


9 


10 


38 


5793 5809 5821 


5832 


5843 


5855 


5866 5877 


5888 


5899 


1 


2 


3 5 


6 


7 


8 


9 


10 


39 


5911 5922 5933 


5944 


5955 


5963 


5977 


5988 


5999 


6010 


1 


2 


34 


5 


7 


8 


9 


10 


40 


6021J6031 6012 


6053 6064 


6075 


6085 


6C96 


6107 


6117 


1 


2 


».« 


5 


6 


8 


9 


10 


41 


6128 6138 6149 


61606170 


6180 


6191 


6201 


6212 


6222 


1 


2 


3 4 


5 


6 


7 


8 


9 


42 


6232 6243 6253 


6263 6274 


6284 


6294 6304 


6314 


6325 


1 


2 


3 4 


5 


6 


7 


S 


9 


43 


6335 6345 6355 


6365 6375 


6385 


6395 6405 


6415 


6425 


1 


2 


3 1 4 


5 


6 


7 


8 


9 


44 


6435*6144 6454 


64646474 


6484 


6493 


6503 


6513 


6522 


i 


2 


V 


5 


6 


7 


8 


9 


45 


6532 6542 6551 


6561 6571 


6580 


6590 


6599 


6609 


6618 


1 


2 


3 4 


5 


6 


7 


8 


9 


46 


6628 6637 6646 


6656 6665 


6675 


6684 


6693 


6702 


6712 


1 


2 


3' 4 


5 


6 


7 


7 


8 


47 


6721 6730 6739 


67496758 


6767 


6776 


6785 


6794 


6803 


1 


2 


3 4 


5 


5 


6 


7 


8 


48 


68126821 '6830 


6839 '6848 


6857 


6866 


6875 


6884 


6893 


1 


2 


3 4 


4 


5 


6 


7 


8 


49 


6902 ! 6911 '6920 


6928 6937 


6946 


6955 


6964 


6972 


6981 


1 


2 


3 4 


4 


5 


6 


7 


8 


50 


6990 6998 7007 


7016 7024 


7033 


7042 


7050 


7059 


7067 


1 


2 


3 3 


4 


5 


6 


7 


8 


51 


7076 7084 7093 


7101 7110 


7118 


7126 


7135 


7143 


7152 


1 


2 


3 3 


4 


5 


6 


7 


8 


52 


71607168,7177 


7185 7193 


7202 


7210 


7218 


7226 


7235 


1 


2 


2 3 


4 


5 


6 


7 


7 


53 


7243 7251 7259 


7267,7275 


7284 


7292 


7300 


7308 


7316 


1 


2 


2 3 


4 


5 


6 


6 


7 


54 


7324 7332 7340 


73487356 


7364 


7372 


7380 


7388 


7396 


1 


2 


2 3 


4 


5 


6 


6 


*'l 



1 

LOGARITHMS OF NUMBERS. 


3 — 





1 


2 


3 


4 


5 


6 


7 


8 


9 


Proportional Parts. 


12 


3 4! 


5 6 


7 8 


9 


55 7404 


7412 


7419 


7427 7435 


7443 


7451 


7459 


7466 


7474 


1 2 


~2~3~ 


4 5 


5 6 


7 


56 7482 


7490 


7497 


7505 7513 


7520 


7528 


7536 


7543 


7551 


1 2 


2 3 


4 5 


5 6 


1 7 


57,7559 


7566 


7574 


7582 7589 


7597 


7604 


7612 


7619 


7627 


1 


2 


2 3 


4 5 


5 6 


! * 


58 ( 7634 


7642 


( 7649 


7657 7684 


7672 


7679 


7686 


7694 


7701 


1 


1 


2 3 


4 4 


5 6 


i 


59*7709 


7716 


7723 


7731 7738 


7745 


7752 


7760 


7767 


7774 


1 


1 


2 3 


4 4 


5 6 

1 


7 


60 ( 778 2 


7789 


7796 


7803 7810 


7818 


7825 


7832 


7839 


7846 


1 


1 


2 3 


4 4 


5 6 


I 
6 i 


61 7853 


7860 


7868 


7875 7882 


7839 


7896 


7903 


7910 


7917 


1 


l 


2 3 


4 4 


5 6 


6 


62 j 7924 


7931 


7938 


7945 7952 


7959 


7966 


7973 


7980 


7987 


1 


1 


2 , 3 


3 4 


5 6 


6| 


63 7993 


8000 8007 


8014.8021 


8028 


8035 


8041 


8048 




1 


1 


2 


3 


3 4 


5 5 


< 


64*8062 
| 


8069 8075 


8082 8089 


8096 


81028109 

1 


8116 


8122 


1 


1 


2 


3 


3 4 


5 5 

I 


6 


65 8129 


3136 8142 


8149 8156 


8162 


81698176 


8182 


8189 


1 


i 


■: 


s 


3 4 


5 5 


6 


66 8195 


82028209 


8215 822-2 


8223 


8235 8241 


82 4S 


8254 


1 


1 


•; 


3 


3 4 


5' 5 


6 


67 8261 


8267 8274 


8280 8287 


8293 


8299 8306 


S3 12 


8319 


i 


1 


•: 


3 


3 4 


5 5 


6 


68 8325 


8331 8333 


3344 8351 


8357 


8363 8370 


8376 


8382 


1 


i 


■; 


| 3 


3 4 


4 5 


6 


69 8388 
■ 


8395 8401 


84078414 


8420 


8426J8432 


8439 


8445 


1 


1 


. 


2 


3 4 


4 5 


6 


70 8451 


8457 8463 


3470 8476 


8482 


8488 8494 


8500 


85C6 


1 


l 
1 


2 


2 


3 4 


A 


5 


6 


7f 8513 


8519 8525 


8531 8537 


8543 


8549 8555 


S561 


8567 


1 


1 


a 


2 


3 4 


A 


5 


5 


72 ' 8573 


8579 8585 


8591 8597 


8603 


8609 8615 


8621 


8627 


1 


1 


■2 


2 


3 4 


4 


5 


5 


73 ' 8633 


8639 8615 


86518657 


8663 


8669 8675 


8681 


66S6 


i 


1 


2 


2 


3 4 


4 


* 


5 


74' 869 2 
| 


8698 


8704 


87108716 


8722 


8727 8733 


8739 


8745 


1 


1 


a 


2 


3 4 


4 


5 


5 


75 8751 


8756 


3762 


8768 8774 


8779 


8785 8791 


8797 


SS02 


1 


|« 


2 


2 


3 3 


4 


, 5 


5 


76' 8808 


8814 


8820 


8825 8831 


8837 


8842 '8848 


8854 


8S59 


1 


1 


2 


2 


3 3 


4 


5 


5 


77^8865 


8871 


8876 


8382 8887 


8893 


8899 8904 


8910 


8915 


1 


1 


2 


|» 


3 3 


4 


4 


5 


78 8921 


8927 


8932 


8938 8943 


8949 


8954 8960 


8965 


8971 


1 


1 


2 


•2 


3 3 


4 


4 


5 


79 8976 


8982 


3937 


8993 8993 


9004 


9009^015 


90:0 


9025 


1 


i 


2 


•2 


3 3 


4 


4 


5 


80 9031 


9036 


9042 


9047 9053 


9058 


9063 9069 


9074 


9079 


1 


1 


■2 


2 


3 3 


4 


4 


5 


81*9085 


9090 


9096 


9101 9106 


9112 


911791-22 


912S 


'•133 


1 


1 


2 


2 


3 3 


4 


4 


5 


82 9138 


9143 


9149 


91549159 


9165 


91709175 


91S0 


9186 


1 


1 


2 


2 


3 3 


4 


4 


5 


83 


9191 


9196 


9201 


9206 9212 


9217 


9222 9227 


9232 


9238 


1 


1 


2 


2 


3 3 4 


4 


5 


84 


9243 


9248 


9253 


9258 9263 

1 


9269 


9274 


9279 


92S4 


9289 


1 


1 


2 


2 


3 3 4 


4 


5 

1 


8 5 


9294 


9299 


9304 


9309 9315 


9320 


9325 


9330 


9335 


9340 


1 


1 


2 


•2 


3 3 4 


4 


• 


85 


9345 


9350 


9355 


9360 9365 


9370 9375 9380 


9385 


9390 


1 


1 


2 


2 


3 3 4 


4 


5 


87 


9395 


9400 


9405 


9110 9415 


9420 9425 9430 


9435 


9440 


1 


1 


a 


2 3 3 


4 


4 1 


88 


9445 


9450 


9455 


9460 9465 


9469 9474 9479 


9484 


94S9 


° 


1 


1 


•2 


2 3 3 


4 


4 


89 


9494 


9499 


9504 


9509 9513 


9518 9523 9528 


9533 


9538 


°i 


1 


1 


2 


2 3 3 


4 


4 


90 


9542 


9547 


9552 


9557 9562 


9566 9571 9576 


9581 


95S6 





1 


1 


2 


2 3 3 


4 


4 


91 


9590 


9595 


9600 


9605 9609 


9614 9619 9624 


96 2S 


9633 





l 


1 


•2 


2 3 3 


4 


4 


92 


9638 


9643 


9647 


9652 9657 


9661 9666 9671 


9675 


96S0 





i 


1 


•2 


2 3 3 


4 


4 


93 


9685 


9689 


9694 


9699 9703 


9708 9713 


9717 


9722 


9727 





1 


1 


•2 ! 


2 3 3 


4 


4 


94 


9731 


9736 


9741 


9745 9750 

1 


9754 9759 


9763 


976S 


9773 





1 


1 


2 


2 3 3 


4 


4 


1 95 


9777 


9782 


9786 


9791 9795 


9800 9805 


9809 


9814 


9S18 





1 


1 


■2 


2 3 3 


4 


4 


96 


9823 


9827 


9832 


9836 9841 


9845 9S50 


9854 


9859 


9S63 





1 


1 


■2 


2 3 3 


4 


4 i 


97 


9868 


9872 


9877 


9881 93S6 


9S90 9894 


9899 


3903 


9908 





1 


1 


•2 


2 3 3 


4 


4 1 


98 


9912 


9917 


99-21 


9926 9930 


9934 9939 


9943 


5948 


9952 





1 


1 


■2 


I 3 3 


4 


4 


99 


9956 9961 


9965 9969 9974 


9978 9933 9987 


9991 


5996 


0' 


1 


1! 


•2 


2 3 3.' 3 4 | 



ANTILOGAKITHMS. 







1 


2 


3 


4 


5 


6 


7 


8 




Proportional Parts. 


9 


1 




2 




3 4 1 5 


6 

1 


1 
2 


8 

2 


9 

2 


.00 


1000 


1002 


1005 


1007 


1009 


1012 


1014 


1016 


1019 


1021 


1 


1 


1 


.01 


1023 


1026 


1028 


1030 


1033 


1035 


1038 


1040 


1042 


1045 








1 


1 


1 


1 


2 


2 


2 


.02 


1047 


1050 


1052 


1054 


1057 


1059 


1062 


1064 


1067 


1069 








1 


1 


1 


1 


2 


2 


2 


.03 


1072 


1074 


1076 


1079 


1081 


1084 


1086 


1089 


1091 


1094 








1 


1 


1 


1 


2 


2 


2 


.04 


1096 


1099 


1102 


1104 


1107 


1109 


1112 


1114 


1117 


1119 





1 


1 


1 


1 


2 


2 


2 


2 


.05 


1122 


1125 


1127 


1130 


1132 


1135 


1138 


1140 


1143 


1146 





1 


1 


1 


1 


2 


2 


2 


2 


.06 


1148 


1151 


1153 


1156 


1159 


1161 


1164 


1167 


1169 


1172 





1 


' 


1 


1 


2 


2 


2 


2 


.07 


1175 


1178 


1180 


1183 


1186 


1189 


1191 


1194 


1197 


1199 





1 


J 


1 


1 


2 


2 


2 


2 


.08 


1202 


1205 


1208 


1211 


1213 


1216 


1219 


1222 


1225 


1227 





1 


1 


1 


1 


2 


2 


2 


3 


.09 


1230 


1233 


1236 


1239 


1242 


1245 


1247 


1250 


1253 


1256 





1 


1 


1 


1 


2 


2 


2 


3 


.10 


1259 


1262 


1265 


1268 


1271 


1274 


1276 


1279 


1282 


1285 





1 


1 


1 


1 


2 


2 


2 


3 


.11 


1288 


1291 


1294 


1297 


1300 


1303 


1306 


1309 


1312 


1315 





1 


1 


1 


2 


2 


2 


2 


3 


.12 


1318 


1321 


1324 


1327 


1330 


1334 


1337 


1340 


1343 


1346 





1 


1 


] 


2 


2 


2 


2 


3 


.13 


1349 


1352 


1355 


1358 


1361 


1365 


1368 


1371 


1374 


1377 





1 




] 


2 


2 


2 


3 


3 


.14 


1380 


1384 


1387 


1390 


1393 


1396 


1400 


1403 


1406 


1409 





1 


1 


1 


2 


2 


2 


3 


3 


.15 


1413 


1416 


1419 


1422 


1426 


1429 


1432 


1435 


1439 


1442 





1 


1 


1 


2 


2 


2 


3 


3 


.16 


1445 


1449 


1452 


1455 


1459 


1462 


1466 


1469 


1472 


1476 





1 


1 


1 


2 


2 


2 


3 


3 


.17 


1479 


1483 


1486 


1489 


1493 


1496 


1500 


1503 


1507 


1510 





1 


1 


1 


2 


2 


2 


3 


3 


.18 


1514 


1517 


1521 


1524 


1528 


1531 


1535 


1538 


1542 


1545 





1 


1 


1 


2 


2 


2 


3 


3 


.19 


1549 


1552 


1556 


1560 


1563 


1567 


1570 


1574 


1578 


1581 





1 


1 


1 


2 


2 


3 


3 


3 


.20 


1585 


1589 


1592 


1596 


1600 


1603 


1607 


1611 


1614 


1618 





1 


1 


1 


2 


2 


3 


3 


3 


.21 


1622 


1626 


1629 


1633 


1637 


1641 


1644 


1648 


1652 


1656 





1 


1 


2 


2 


2 


3 


3 


3 


.22 


1660 


1663 


1667 


1671 


1675 


1679 


1683 


1687 


1690 


1694 





1 


1 


2 


2 


2 


3 


3 


3 


.23 


1698 


1702 


1706 


1710 


1714 


1718 


1722 


1726 


1730 


1734 





1 


1 


2 


2 


2 


3 


3 


4 


.24 


1738 


1742 


1746 


1750 


1754 


1758 


1762 


1766 


1770 


1774 





1 


1 


2 


2 


2 


3 


3 


4 


.25 


1778 


1782 


1786 


1791 


1795 


1799 


1803 


1807 


1811 


1816 





] 


1 


2 


2 


2 


3 


3 


4 


.26 


1820 


1824 


1828 


1832 


1837 


1841 


1845 


1849 


1854 


1858 





1 


1 


2 


2 


3 


3 


3 


4 


.27 


1862 


1866 


1871 


1875 


1879 


1884 


1888 


1892 


1897 


1901 





1 


1 


2 


2 


3 


3 


3 


4 


.28 


1905 


1910 


1914 


1919 


1923 


1928 


1932 


1936 


1941 


1945 





1 


1 


2 


2 


3 


3 


4 


4 


.29 


1950 


1954 


1959 


1963 


1968 


1972 


1977 


1982 


1986 


1991 





1 


1 


2 


2 


3 


3 


4 


4 


.30 


1995 


2000 


2004 


2009 


2014 


2018 


2023 


2028 


2032 


2037 





I 


1 


2 


2 


3 


3 


4 


4 


.31 


2042 


2046 


2051 


2056 


2061 


2065 


2070 


2075 


2080 


2084 





1 


1 


2 


2 


3 


3 


4 


4 


.32 


2089 


2094 


2099 


2104 


2109 


2113 


2118 


2123 


2128 


2133 





1 


1 


2 


2 


3 


3 


4 


4 


.33 


2138 


2143 


2148 


2153 


2158 


2163 


2168 


2173 


2178 


2183 


c 


1 


1 


2 


2 


3 


3 


4 


4 


.34 


2188 


2193 


2198 


2203 


2208 


2213 


2218 


2223 


2228 


2234 




1 


2 


2 


3 


3 


4 


4 


5 


.35 


"2239 


2244 


2249 


2254 


2259 


2265 


2270 


2275 


2280 


22S6 




! 1 


2 


2 


3 


3 


4 


4 


5 


.36 


2291 


2296 


2301 


2307 


2312 


2317 


2323 


2328 


2333 


2339 




1 


2 


2 


3 


3 


4 


4 


5 


.37 


2344 


2350 


2355 


2360 


2366 


2371 


2377 


2382 


2388 


2393 




1 


2 


2 


3 


3 


4 


4 


5 


.38 


2399 


2404 


2410 


2415 


2421 


2427 


2432 


2438 


2443 


2449 




1 


2 


2 


3 


3 


4 


4 


5 


.39 


2455 


2460 


2466 


,2472 


2477 


.2483 


2489 


2495 


2500 


2506 




1 


2 


2 


3 


3 


4 


5 


5 


.40 


2512 


2518 


2523 


2529 


2535 


2541 


2547 


2553 


2559 


2564 




1 


2 


2 


3 


4 


4 


5 


5 


.41 


2570 


2576 


2582 


2588 


2594 


2600 


2606 


2612 


2618 


2624 




1 


2 


2 


3 


4 


4 


5 


5 i 


.42 


2630 


2636 


2642 


,2649 


2655 


2661 


2667 


2673 


2679 


2685 




] 


2 


2 


3 


4 


4 


5 


6 


.43 


2692 


2698 


2704 


2710 


2716 


2723 


2729 


2735 


2742 


2748 




1 


2 


3 


3 


4 


4 


5 


6 


.44 


2754 


2761 


2767 


2773 


2780 


2786 


2793 


2799 


2805 


2812 




1 


2 


3 


3 


4 


4 


5 


6 i 
1 


.45 


28 IS 


2825 


2831 


2838 


2844 


2851 


2858 


2864 


2871 


2877 




! i 


2 


3 


3 


4 


5 


5 


6 


.46 


2884 


2891 


'2897 


2904 


2911 


2917 


2924 


2933 


2938 


2944 




! 1 


2 


3 


3 


4 


5 


■ 


6 


.47 


2951 


2958 2965 


2972 


12979 


2985 


2992 


2999 


3006 


3013 




1 1 


2 


3 


; 3 


4 


* 


■ 


6| 


.48 


302C 


3027 3034 


3041 


3048 


3055 


3062 


3069 


3076 


3083 




1 


2 


3 


4 


4 


5 


6 


6 i 


.49 


J309C 


3097 


310c 


3112 


3119 


3126 


(3133 


3141 


3148 


3155 




' 1 


2 


3 


■ 4 


4 


5 


6 


•1 



f -- .. —1 

ANTILOGARITHMS. 


si 





1 


2 


3 


4 


5 


6 


7 


8 


9 


Proportional Parts. 


1 


2 


3 4 5 


6 


7 


8 


9 


.50 


3162 


3H0 


3177 


3184 3192 


3199 


3206 


3214 


3221 


3228 


i 


i 


23 4 


4 


5 


6 


7 


.51 


3236 


3243 3251 


3258 3266 


3273 


3281 


3289 


3296 


3304 


i 


2 


2 3 


4 


5 


* 


■ 


7 


.52 


3311 


3319 3327 


3334 3342 


3350 


3357 


3365 


3373 


3381 


i 


2 


2 3 


4 


5 


• 


■ 


7 


.53 


3388 


3396 3404 


3412 342C 


3428 


3436 


3443 


3451 


3459 


i 


2 


2 3 


4 


5 


6 


6 


7 


.54 


3467 


3475 3483 


3491 3499 


3508 


3516 


3524 


3532 


3540 


i 


2 


2 3 


4 


5 


6 


6 


7 


.55 


3548 


3556 3565 


3573 


3581 


3589 


3597 


3606 


3614 


3622 


i 


2 


a' 3 


4 


5 


6 




7 


.56 


3631 


3639 36^8 


3656 


3664 


3673 


3681 


3690 


3698 


3707 


i 


2 


S3 


4 


5 


6 


1 


8 


.57 


3715 


3724 3733 


3741 


3750 


3758 


3767 


3776 


3784 


3793 


i 


a 


3 3 


4 


■ 


6 


7 


8 


.58 


3S02 


38113819 


3828 


3837 


3846 


3855 


3864 


3873 


3882 


i 


2 


3 4 


4 


5 


6 


7 


8 


.59 


3890 


3899 3908 


3917 


3926 


3936 


3945 


3954 


3963 


3972 


i 


2 


3 4 


5 


* 


6 


7 


8 ■" 


.60 


3981 


3990 3999 


4C09 


4018 


4027 


4036 


4046 


4055 


4064 


i 


2 


3 4 


5 


6 


- 


7 


8 


.61 


4074 


4083 4093 


4102 


4111 


4121 


4130 


4140 


4150 


4159 


i 


2 


3 4 


5 


6 


' 


8 


9 


.62 


4169 


41784188 


4198 


4207 


4217 


4227 


4236 


4246 


4256 


i 


2 


3 4 


5 


6 


7 


8 


.9 


.63 


4266 


4276 4285 


4295 


4305 


4315 


4325 


4335 


4345 


4355 


i 


2 


34 


5 


6 


7 


8 


9 


.64 


4365 


4375 


4385 


4395 


4406 


4416 


4426 


4436 


4446 


4457 


i 


2 


3 4 


S 


6 


7 


8 


9 


.65 


4467 


4477 


4487 


4498 


4508 


4519 


4529 


4539 


4550 


4560 


i 


2 


3 4 


5 


6 


7 


8 


9 


.66 


4571 


4581 


4592 


4603 


4613 


4624 


4634 


4645 


4656 


4667 


i 


2 


3 4 


5 


6 


7 


9 


10 


.67 


4677 


4688 


4699 


4710 


4721 


4732 


4742 


4753 


4764 


4775 


i 


2 


3 4 


5 


7 


8 


9 


10 


.68 


4786 


4797 


4808 


4819 


4831 


4842 


4853 


4864 


4875 


4887 


i 


2 


3 4 


6 


7 


8 


9 


10 


.69 


4898 


4909 


4920 


4932 


4943 


4955 


4966 


4977 


4989 


5000 


i 


2 


3 5 


6 


7 


8 


9 


10 


.70 


5012 


5023 


5035 


5047 


5058 


5070 


5032 


5093 


5105 


5117 


i 


2 


J 5 


6 


7 


8 


9 


11 


.71 


5129 


5140 5152 


5164 


5176 


5188 


5200 


5212 


5224 


5236 


i 


2 


4 ! 5 


6 


7 


8 


10 


11 


.72 


5248 


5260 5272 


5284 


5297 


5309 


5321 


5333 


5346 


5358 


i 


2 


4 5 


6 


7 


9 


10 


11 


.73 


5370 


5383 5395 


5408 


5420 


5433 


5445 


5458 


5470 


5483 


i 


3 


4 5 


6 


8 


9 


10 


11 


.74 


5495 


5508 


5521 


5534 


5546 


5559 


5572 


5585 


5598 


5610 


i 


3 


4 5 


6 


8 


9 


10 


12 


.75 


5623 


5636 


5649 


5662 


5675 


5689 


5702 


5715 


5728 


5741 


i 


3 


1 
4 5 


7 


8 


9 


10 


12 


.76 


5754 


5768 


5781 


5794 


5808 


5821 


5834 


5848 


5861 


5S75 


i 


3 


4 5 


7 


8 


9 


11 


12 


.77 


5888 


5902 


5916 


5929 


5943 


5957 


5970 


5984 


5998 


6012 


i 


3 


4 5 


7 


8 


10 


11 


12 


.78 


60 26 


6039 


6053 


6067 


6081 


6095 


6109 


6124 


6138 


6152 


i 


3 


4 6 


7 


8 


10 


11 


13 


.79 


6166 


6180 


6194 


6209 


6223 


6237 


6252 


6266 


6281 


6295 


i 


3 


4 


6 


- 


9 


10 


11 


13 


.80 


6310 


6324 


6339 


6353 


6368 


6383 


6397 


6412 


6427 


6442 


i 


3 


4 


6 


7 


9 


10 


12 


13 


.81 


6457 


6171 


6486 


6501 


6516 


6531 


6546 


6561 


6577 


6592 


2 


3 


5 


6 


E 


9 


11 


12 


14 


.82 


6607 


6622 


6637 


6653 


6668 


6683 


6699 


6714 


6730 


6745 


2 


3 


5 


6 


8 


9 


11 


12 


14 


.83 


6761 


6776 


6792 


6803 


6823 


6839 


6855 


6871 


6887 


6902 


2 


3 


5 


6 


8 


9 


11 


13 


14 


.84 


6918 


6934 


6950 


6966 


6982 


6998 


7015 


7031 


7047 


7063 


2 


3 


5 


6 


8 


10 


» 


13 


15 


.85 


7079 


7096 


7112 


7129 


7145 


7161 


7178 


7194 


7211 


7228 


2 


3 


5 


7 


8 


10 


12 


13 


15 


.86 


7244 


7261 


7278 


7295 


7311 


7328 


7345 


7362 


7379 


7396 


2 


3 


5 


' 


8 


,0 


12 


13 


15 


.87 


7413 


7430 


7447 


7464 


7482 


7499 


7516 


7534 


7551 


7568 


2 


3 


5 


7 


9 


10 


12 


14 


16 


.88 


7586 


7603 


7621 


7638 


7656 


7674 


7691 


7709 


7727 


7745 


2 


4 


5 


7 


9 


11 


12 


14 


16 


.89 


7762 


7780 


7798 


7816 


7834 


7852 


7870 


' 


7907 


7925 


2 


4 


5 


7 


9 


11 


13 


14 


16 


.90 


7943 


7962 


7980 


7998 


8017 


8035 


8054 


8072 


8091 


8110 


2 


4 


6 


7 


9 


11 


13 


15 


17 


.91 


8128'8147 


8166 


8185 


8204 


8222 


8241 


8260 


8279 


8299 


2 


4 


6 8 


9 


11 


13 


15 


17 


.92 


83 18 '8337 


8356 


S375 


8395 


8414 


8433 


8453 


8472 


8492 


2 


4 


6 8 


10 


12 


14 


15 


17 


.93 


3511 


S531 


8551 


8570 


3590 


8610 


8630 '8650 


8670 


8690 


2 


4 


6 8 


10 


12 


14 


16 


18. 


.94 


8710 8730 


8750 


8770 


8790 


8810 


883 1[ 8851 


8872 


8892 


2 


4 


6 


8 


10 


12 


14 


16 


18 


.35 


8913 8933 


8954 


8974 


S995 


9016'9036'9057 


9078 


9099 


2 


4 


6 


8 


10 


12 


15 


17 


19 


.96 


9120 9141 


9162 


9183 


9204 


922692479268 


9290 


9311 


2 


4 


6 


8 


11 


13 


15 


17 


19 


.97 


9333 9354 


9376 


9397'9419 


94419462 9484 


9506 


9528 


2 


4 


7 


9 


11 


13 


15 


17 20 


.98 


9550 9572 


9594 


9616 9638 


9661 9683 9705 


9727 


9750 


2 


4 


7 


9 


1] 


13 


16 


18 20 


.99 


9772 9795I9S17 


9840 9863 


9S86 9908 9931 


9954 


9977 


2 


5 


7 


9 


11 


14 


16 


18 20 



CONSTANT LOGARITHMS. 

Loga- Ar. Co. 

ritJnns. Log. 

Circumf. of circle when R= 1, {~ = 1.5708) 0.1961 9.8039 

" " " " D=l, {it = 3.1416) 0.4971 9.5028 

Area of circle when Br = 1, (n = 3.1416) 0.4971 9.5028 

" " « " D 2 =l, (~ = 0.7854) 9.8951 0.1049 

" " « * C 2 =l, (~= 0.0796) 8.9008 1.0992 

Surface of sphere when R 2 = 1, (4^=12.5664) 1.0992 8.9008 

" " " " D 2 =l, (tv = 3.1416) 0.4971 9.5028 

" " " « C*= 1, (- = 0.3183) 9.5028 0.4971 

Solidity of sphere when R z = 1, (|^= 4.1888) 0.6221 9.3779 

o 

" " " " 2F=1, Q = 0.5236) 9.7190 0.2810 

" " " " C 3 =l, (^= 0.0169) 8.2275 1.7724 

Weight of one litre of Hydrogen (0.0896 grammes) 8.9522 1.0478 

" " " " "Air (1.293 " ) 0.1116 9.8884 

« " " " " " (14.43 criths ) 1.1594 8.8406 

Per cent of Oxygen in air by weight (0.2318) 9 3651 0.6349 

" " "Nitrogen" " « " (0.7682) 9.8855 1145 

Mean height of Barometer (76 cm.) 1.8808 8.1192 

Coefficient of expansion of Air (0.00366) 7.5635 2.4365 

Latent Heat of Water (79) 1.8976 8.1024 

« « u Yree Steam (537) 2.7300 7.2700 

To reduce Gp.(gr. to S P- Gr., or reverse, add to log. 1.1594 or 8.8406 

" " Sp. Gr. to Sp. Gr., " " " " " 5.9522 or 4 0478 

u " 6p.(^r. toSp.Gr., " " " " " 7.1116 or 2.8884 

" " grammes to criths, " " " " " 1.0478 or 8.9522 



INDEX 



The numbers of this Index refer to pages ; those following dashes are references to 
reactions, into which the given substance enters as an important factor. To use the 
index with copies of the first edition, add ten to the number of all pages above the two 
hundredth. 



Acetamide, 243- — 245. 

Acetic Acid, 74, 438, 433. —513. 

" Anhydride, 433. 

" Ether, 492. — 61, 493. 
Acetine, 517- 
Aceto-lactic Acid, 510. 
Acetone, 495. 
Acetonyl, 484. 
Acetyl, 73, 434. 

" Chloride, — 57, 493. 
Acetylene Series, 477, 433. 
Acidity of Bases, 94. 
Acids, Definition of, 83. 
Acid Radicals, 83. 

" Salts, 87. 
Aconitic Acid, 513. 
Acrolein, 493. 
Acryl, 484. 
Acrylic Acid, 493. 

" Series, 493. 

" " Secondary AcitK 439. 

" " Tertiary Acids, 500. 

Adhesion, 12, 37. 
Adipic Acil, 512. 
Agalmatolite, 410. 
Agate, 445 
Alabaster, 342. 
Allbite, 409. 
Albumen, 524. 

Alcohol, 9J, 435, 487. — 33, 77, 358, 455, 
491, 492, 509, 512. 

" Diglyceric, 517. 

" Iso, 493. 

Pseulo, 483, 493. 

" Radicals, 73 

" Secondary, 493. 

" Tertiary, 437- 

" Tetratomic, 519. 

" Triatomic, 515. 

" Triglycevic, 517. 
Aldehyde, 437, 434. — 509. 
Alkali, Definition of, 81. 

" Fixed, 247. 

" Volatile, 247. 
Alkaline Sulphides, 312. 

" Sulp hohydrates, 312. 
Allotropism, 1&3. — 251, 332, 308, 460. 
Allyl, 78, 4m, 4S1. 
Allylic Alco'iol, 497. 

" Iodide, — 481, 497. 

" Cyanide, — 500. 
Allylene, 477. 
Altaite, 321. 

Alums, 319, 373, 400, 409, 412. 
Alumiuates, 414. 
Aluminic Acetate. 413. 

" Chloride, 414, 415. 



Aluminic Hydrate, 408, 414. 

" Nitrate, 414. 

" Oxide, 415. 

" Sulphate, 409, 413, 414. 

" Sulphide, 415. 
Aluminite, 409. 
Aluminum, 408. — 412. 
" Bronze, 411. 

Alum-stone, 409. 
Alunite, 409. 
Alunogen, 409. 
Amethyst, 445. 
Amides, 243. 
Amidogen, 39, 243. 
Amines, 242. 

Ammonia, 82, 240. — 33, 33, 82 , 233, 246, 491 
Ammonic Carbonates, 248. — 243, 341. 

" Chloride, 247. — 33, 241. 

" Dichromate, — 399. 

" Nitrate, — 239. 

" Nitrite, —233. 

" Silico-fluoride, 452. 

" Sulphohydrate. 312. 

" Sulphide, 311 , 312. — 331. 
Ammonides, 242. 
Ammonio-cobalt Bases. 339. 
Ammonio-magnesic Phosphate. 356. 
Ammonio-manganous Salts, 3i4. 
Ammonio-platinous Chloride. 427. 
Ammonio-platinic Chloride, 426. 
Ammonio-platinum Bases, 423. 
Ammonio-stannic Chloride, 435. 
Ammonium, 82, 246. 

Alum, 409, 413. 
" Bases. 248. 

" Compounds, 245. 

Ampere's Law, 17. 
Amygdaline, 522. 
Amylaceous Bodies, 521. 
Amylene, 477. 
Amyl, 72, 484. 
Amylic Alcohol, 486. 
" Acetate, 492. 
41 Glycerine, 518. 
" Hydride, 477. 
" Acid Sulphate,— 492. 
Amy loses, 521. 
Analcime, 410, 456, 457. 
Analysis, 9. 

Analytical Reaction, 35. 
Anchoic Acid, 512. 
Andalusite. 409. 
Andesine, 457. 
Angelic Acid, 498. 
Anglesite, 346. 
Anhydrides Acid, 85 

" Basic, S2. 

" of Organic Acids, 493. 

Anhydrite, 342. 



INDEX. 



Aniline, 242, 482. — 502. 

Animal Kingdom, Province of, 525. 

Ankerite, 378. 

Annabergite, 335. 

Anorthite, 409, 456. 

Antimoniate of Antimony, 270. 

Antimonic Acid. 269. 

Anhydride, 270. 
Chloride, 267. 
" Sulphochloride, 267. 
Sulphide, 275. 
Antimonious Bromide, 267. 

" Chloride, 266. — 268, 270. 

" Fluoride, 237. 

" Hydrate, —61. 

" Iodide, 237. 

11 Oxide, 237. — 264. 

" Sulpaate, — 265 

" Su.phide, 272. -264,266,310. 

Antimoniuretted Hydrogen, 270. 
Antimony, 284. — 265, 236. 
Butter of, 266. 
" and Alco.iol Radicals, 271. 
" " Chlorine, 266. 

" " Hydrogen, 270. 

" " Oxygen, 267. 

" " Sulphur, 272. 

" " Zinc, 271. 

" Glance, 234, 272. 
" Oxychloride of, 263. 
Antozone, 304. 
Antozonides, 305. 
Apatite, 291, 343. 
Apjohnite, 409. 
Aqua Ammonia, 247. 

" Regia, 224. 
Arachidic Acid, 488. 
Ara^onite, 3±0. 
Argentic Bromide, 221. 
" Chloride, 221. 
" Iodide, 221. 

" Nitrate, 220. — 33, 38, 56, 233. 
[ " Oxalate, — 455. 
" Oxide, 222. — 249. 
" Peroxide, 222. 
" Sulp'iate, — 54. 
" Sulphite, —315. 
Arsenic, 257. 

" Acid, 259. 

" and Alcohol Radicals, 261. 
" " Chlorine, 263. 
" " Hydrogen, 260. 
" " Iodine, 263. 
" " Sulphur, 233. 
" Anhydride, 230. 
" Compounds with Bromine, 263. 
Arsines, 231. 
Arsenide of Tin, —260. 
Arsenious Anhydride, 258. — 257. 
" Bromide and Iodide, 263. 
" Sulphide, 263. 
Arsenites, 259. 

Arseniuretted Hvdrogen, 260. 
Artiad Elements, 300. 
Artiads, Definition of, 59. 
Atacamite, 331. 
Atmosphere, 114. 
Atomicity, 55. 

" of Acids, 93. 
" of Ridicais,59. 
Atomic Ratio, 448. 
" Weight, 25, 28. 



Atomic Weights, Relations of, 195. 
Atoms, Definition of, 24. 

" Negative, 168. 

" Positive, 168. 

" Quantivalence_of, 59, 132. 

" True Idea of, 70. 
Atom-fixing Power, 57. 
Augite, 356. 
Auric Salts, 224. 
Auriferous Quartz, 222. 
Aurous Salts, 224. 
Axinite, 228. 
Azurite, 330. 



B. 



Baric Chloride, 344. — 33. 

" Hydrate, 345. — 82. 

" Nitrate, 344. 

" Oxide, 345. —35. 

" Peroxide, 345. — 203. 

" Sulphide, —345. 
Bario-platinic Chloride, 426. 
Bario-stannous Chloride, 435. 
Barium. 344. 
Bases, Definition of, 80. 
Basic Ferric Hydrates, 386. 

" Radicals, 83. 

" Salts, 87. 
Basicity of Acids, 93, 435. 
Beauxite, 408. 
Behenic Acid, 488. 
Benzamide, 76, 243. 
Benzine, 482. 

Benzoic Acid, 501, 503. — 482. 
" Alcohol, 501. 
" Ether, 493. 
Benzoin Gum, 503. 
Benzol, 477, 482. — 235. 
Benzoyl, 503. 
Berthierite, 273. 
Beryl, 333,455. 
Berzelianite, 320. 
Bessemer Process, 3S2. 
Bismuth, 275. 

" and Alcohol Radicals, 276. 
" Basic Nitrate, 278. 
" Compounds with Oxygen, 277. 
" " " Sulphur, 278. 

" Glance, 275. 
" Magistery of, 278. 
" Oxychloride of, 276. 
Bismuthic Compounds, 277. 
Bismuthous Compounds, 276, 277, 278. 
Black Ball, 214. 
Blast Furnace, 380. 
Bleaching, 207, 314. 

" Powder, 341. 

Blende, 357. 
Bloom, 380. 
Bloomery Forge, 380. 
Blue Pill, 333 
Blue Vitriol, 329. 
Bog Ore, 378. 
Bone Black, 458. 
Boracite, 232. 
Borax, 230. — 229. 
Boric Acid, 229. — 86. 

" Anhydride, 83, 229. — 228, 231. 

" Bromide, 231. 

" Chloride, 231. 

" Fluoride, 231. . 



INDEX. 



ill 



Boric Sulphide, 232. 
Borofluoric Acid, 231. 
Boron, 228. 
Botryogen, 379. 
Bournonite, 273. 
Brackets, Use of, 74. 
Braunite, 373. 
Breithanphite, 335. 
Bricks, 411. 
Britannia Metal, 266. 
Brochantite, 330. 
Bromhydrine, 505. 
Bromine, 210 — 499, 504. 
Bromoform, 494 
Brookite, 430- 

Brown Clay Iron Stone, 378. 
Brown Hematite, 378. 
Brucite, 354. 
Brunswick Green, 331. 
Bunsenite, 335 
Bunsen's Cell, 164. 
Burning, 114. 
Butyl, 484. 
Butylic Alcohol, 485. 

44 Glycol, 505. 

" Hydride, 477. 
Butylene, 477. 
Butyric Acid, 488. 

" Anhydride, 493. 

" Ether, 492. 

" Butyryl, 484. 



C. 

Cacoxenite, 379. 
Cadmio-Zirconic Fluoride, 440. 
Cadmium, 359. 
Caesium, 217. 
Calamine, 357 
Calcareous Marl, 340. 
Calcic Acetate, — 495. 

44 Carbonate, 340. — 344. 

" Chloride. 343. 

44 Chromate, 403. 

" Fluoride. 343. — 207, 452. 

" Hydrate, 341. — 82, 96, 313. 

" Hyposulphite, 315. 

" Nitrate, 344. 

" Oxalate, — 464. 

" Oxide, 341. 

" Peroxide, 342. 

«' Persulphide, 313. 

11 Phosphate, 343.— 250. 

" Silicate, 343 

44 Sulphate, 342. —313. 

" Sulphide, 313. 

4 ' Sulphite, 315. 
Calcined Magnesia, 354. 
Calcite, 340 
Calcium, 340. 
Calomel, 334. 
Calorific Intensity, 119. 

" Power, 118, 122. 
Cane Sugar, 521. 
Capric Acid, 488. 
Caproic Acid, 488. 
Caprylic Acid, 488. 
Carbolic Acid, 502. 
Carbon, 458. — 115, 467. 
Carbonic Acid, 462. 

41 Anhydride, 461. —465. 



Carbonic Chloride — 478. 

44 Oxide, 462.— 463. 

" Sulphide, 466. — 478. 
Carbonyl, 39, 463, 484. 
Carnallite, 216. 
Carnelian, 445. 
Carre's Apparatus, 241. 
Cassiterite, 433. 
Caustic Potash , 216. 

41 Soda, 214. 
Celestine, 344. 
Cementation, 382. 
Cerite, 364. 
Cerium, 364. 
Cerotene, 477. 
Cerotic Acid, 488. 

" Alcohol, 486. 
Cerusite, 346. 
Cervantite, 270. 
Cetene, 477. 
Cetylic Alcohol, 486. 
Chabazite, 410. 
Chalcostibite, 273. ' 
Chalcotrichite, 329. 
Chalcedony, 445. 
Chalk, 340. 

Chameleon Mineral, 377. 
Charcoal, 458. 

" Animal, 458. 
Chemical Change, Characteristics of, 3,110. 
Chemistry, Definition of, 3 
Chili Saltpetre, 215. 
Chinese AVax, 488. 
Chiolite, 408. 
Chloanthite, 365. 
Chloracatic Acid, 67. 
Chlorhydrines, 402, 504, 516. 
Chloric Acid, 209. 

" Peroxide, 209. 
Chlorine, 207. — 208, 231, 233, 341, 399, 452, 
471, 493. 

" Compounds with Oxygen, 209. 
Chlorite, 356, 410. 

Chlorochromic Anhydride, 404. — 399. 
Chloroform, 494. — 38, 57. 
Chlorous Acid, 209. 

44 Anhydride, 209. 
Choke Damp, 461. 
Chromates, 402. 
Chromatic Spectra, 176. 
Chrome Alum, 400. 

Green, 399, 404. 

'« Iron, 398. 

44 Orange, 403. 

44 Yellow, 403- 
Chromic Anhydride, 404. 

44 Chlorhydrines, 402. 

" Chloride, 401. 

" Fluoride, 405 

" Hydrates, 400, 82. 

" Nitrate, 401. 

" Oxalates, 401. 

44 Oxides, 399. 

" Sulphates, 400. 

44 Sulphides, 405. 
Chromite, 398. 
Chromium, 398. 
Chromous Chloride, 398. 
*• Hydrate, 399. 
Chrysoberyl, 363, 408. 
Chrysolite, 356. 
Cinnabar, 332. 



IV 



INDEX. 



Cinnamene, 483. 
Cinnamic Acid. 503. 
Citraconic Add. 514. 
Citric Acid, 519. 
Classification, Grounds of, 192. 
Scheme of, 193. 
Clay Iron Stone, 378. 
Clays, 410. 
Cleavage, 152. 

" Eminent, 152. 
Coal, 458. 
Cobalt, 387. 

" Ammonio-Bases, 369. 
and Oxygen, 368. 
Bloom, 338.' 
Vitriol, 338. 
Cobalticyankles, 370. 
Cobaltine, 338. 
Coefficient of Expansion, 14. 

" " Absorption, 109. 

Cohesion, 12. —37. 
Coke, 459. 
Colcothar, 388. 
Colloids. 111. 
Color, 175. 
Columbite, 293. 
Columbium, 296. 

Compounds of, 296, 297. 
Combustion, 114. 

" Heat of, 117. 

Common Salt, 213 
Compound, Definition of, 7, 10. 

Radicals, 38, 83. 
Compounds, Classes of, 62, 80, 101. 
Conine, 249. 
Copiapite, 379. 
Copper, 328. 

" Ammoniated Compounds, 331. 
" Compounds with Oxygen, 329. 
" Fluohydrate, 331. 
" Glance, 330. 
" Pyrites 328, 330. 
" Salts. 329. 
Coquimbite, 379. 
Corrosive Sublimate, 335. 
Corundum , 408. 
Covelline. &30. 

Cream of Tartar, 217. —214, 268. 
Creosote, 502 
Cresylic Alcohol, 503. 
Crith, 2. 
Crocoite, 398. 
Crocus Martis, 388. 
Crotonic Acid, 498. 
Crotonylene, 477. 
Cryolite, 207, 408. 
Crystalline Axes, 138. 
" Form, J 38. 

" " Identity of, 146. 

<; Structure, 152. 

" Symmetry, 137. 

" Systems, 138. 

Crystalloids, 111. 
Crystals, Irregularities of, 148. 
'* Modifications on, 143. 
Twin, 150. 
Cumin, Essential Oil of, 501. 
Cuminic Acid, 501, 503. • 

Aldehyde, 501. 
Cumol, 477. 
Cumylic Alcohol, 501. 
Cupellation, 220. 



Cupric Carbonates, 330. 

l - Chlorides, 331. 

" Hydride, 331. 

" Mtratts, 330. 

" Oxide, 319. — 84. 

" Oxychloride, 331. 

" Phosphate, 330. 

" Silicate, 330. 

" Silico-fiuoride, 452. 

" Sulphate, 3^9. — 54. 

«« Sulphides, 330. 
Cuprous Chloride, 331. 
Current, Electric, Negative, 157. 
" " Positive, 157. 

" " Strength of, 160. 

" " Unit of, 169. 

Cyanates, 472. 
Cyanetholine, 473. — 77. 
Cyanhydrine, 505. 
Cyanic Acid, 471 — 77. 

" Ethers, 472. — 77. 
Cyanides, 468. 
Cyanite. 409. 
Cyanogen, 466. 

" Compounds with Chlorine, 471. 
Cyanuric Acid, 471. 
Cymol, 477. 



B. 



Danburite, 228. 

Dark Red Silver Ore, 220. 

Datholite. 228 

Definite Proportions, Law of, 9. 

Dextrose, 522. 

Dialysis, 112. 

Diammonic-ferric Sulphate, 386. 

Diamond, 459. 

Diaspore, 4<»8. 

Diatomic Acids, 93, 507- 

Dibasic Acids, 93, 168, 512. 

Dibromhydrine, 505. 

Dichlorhydrine, 516. 

Dicyanic Acid, 471. 

Didymium, 334. 

Diethoxalic Acid, 511. 

Diffusion Gaseous, 112. 

" Liquid, 110. 
Dimethoxalic Acid, 511. 
Dimetric System, 139. 
Dimorphism, 135, 252, 335. 
Dinitro-berzol, 482. 
Dioptase, 330. 
Diplumbic Chromate, 403. 
Disassociation, 128, 325 Prob. 38, 339 Prob. 

30. 
Disinfectants, 207, 314. 
Dolomite, 355 
Drummond Light, 341. 
Dufrenite, 379. 
Dufrenoysite, 263. 
Dutch Oil, 479. 



E. 



Earthen "Ware, 411. 
Earthy Cobalt, 368. 
Electrical Conducting Power, 157. 

" Resistance, 157, 169. 
Electric Current, 156, 160, 169. 
Electricity, 155. 

" Intensity of, 161. 



INDEX. 



Electricity, Quantity of, 161. 
Electrolysis, 165. 

Electromotive Force, 159, 160, 169. 
Unit of, 169. 
Electroplating, 137, 221. 
Elements, 7 

" Classes of, 192. 
" Distribution of, 8. 
" In livi luality of, 70, 190. 
Emerald Nickel, 335. 
Emery, 408. 
Emplectite, 279. 
Enargi e, 2 33. 
Epidote, 410, 456. 
Epsom Silts, 355. 
Equivalency, Chemical, 54. 
Equivalents, 54. 
Erbium, 333. 
Erubescite, 330. 
Erythrite, 3 38,519. 
Etheric Acids, 508. 

" " Secondary, 510. 

Etherification, 401. 
Ethers, 00, 401. — 492. 
" Compound, 492. 
" Hiloid, 493. 
" of Gl.cerine, 517. 
" Mixed, 492 
Ethomethoxaiic Acid, 511. 
Ethyl, 484 

Ethylamine, 58, 242, 245, 472. 
Ethyl-glycollic Aril, 511. 
Ethyl-lactic Acid, 510. 
Ethy.ic Acetate, — 491. 
" Alcohol, 435. 

Chlorile, — 492. 
" Cvanide, — 489. 
" Glycol, 505. 
" II dride, 477. 
" Iodide. —479, 494. 
lC Sulphate, —491. 
Ethylene, 477 — 479, 480, 504, 508. 

Bromide, 479. — 61, 480, 506. 
Bromhydrine, 505. — 506, 507. 
Chloride, 479. 
" Cvanhvdvine, 505. — 509. 
E bier ,"505. 
Glycols, 506. 
" Iolile, 479. 
" Oxide, 505 
Ethylidene Chloride, 509. 

" Cyanhydrine, 510. 

Ethvline, 517. 
Essential Oil of Cumin, 501. 

" Oi's 477, 481. 
Eudialyte. 439 
Eaxenite,29>, 441. 
Exchanges, Theory of, 189. 
Expansion by Heat, 14. 



Fat Acids, 90, 487. 
" " . Isomers of, 491. 
Fats, 518. 
Fayante, 379. 
Feldspars, 409. 
Fergusonite, 293. 
Fermentation, 523. 
Ferrates. 3^9 
Ferric Acetate, 386. 
" Arseniates, 379. 



Ferric Chloride, 386, 387. ~ 470. 
" Ferrocv anile, 4(0. 

" Hydrates, 318,386. 

" Nitrate, 386. 
" Oxalate, 383. 
" Oxide. 3,8,388. — 469. 

" Silicates, 3,9 

; ' Sulphite, 3(9. 386. 

" Sulphides, 3,8, 388. 
Ferricyanides, 4 TO. 
Ferrocyanidts, 439. 
Ferrous Carbonate. 378. 384. 

" Chloride. £85, 387. — 238, 470. 

" Ferric Oxide, 3 ('8, 388. 

" Hydrate. 835,82. 

" Nitrate. 385. 

" Oxalate. 385. 

" Oxide, 338. 

" Phosphate. 385. 

" Sulphate, 3 3h. —226. 

" '' inpotassic, 393. 

« Sulphide, 888. — 309, 459. 
Fibroferrite, 379. 
Fire Damp, 4(8. 
Flint, 445. 
Float Stone. 445. 
Fluorine, 207- 
Fluor Spar, 343, 207. 
Formic Acid. 483, 490. — 464, 514. 
b'ormyl, 484 
Forsterite. 457. 
Fowler"s Solution, 259. 
Franklinite, 3 78. 
Freieslebenite, 273. 
Fumaric Acid, 514. 

" Series, 514. 
Fusible Alloy, 276. 

G. 

Gadolinite, 333, 441. 

Gahnite, 408. 

Galena, 316. 

Gallic Acid, 523. 

Galvanic Battery, 161. 

Garnet, 410, 448, 457. 

Gaseous State, 12. 

Gases, Molecular Condition of, 17. 

Gas, Illuminating, 478. 

Gay Lussac's Law, 48. 

Genthite, 335 

Germau Silver, 336. 

Gibbite, 408. 

Gilding, 226. 

Glass, 214. 216, 447. 

Glaucodot, 338. 

Glockerite, 379. 

Glucinum,333. 

Glucose, 521 . — 524. 

Glucoside, 522. 

Glyceric Acid, 516. 

Glycerides. 518 

Glycerine, 93, 515. — 497. 498, 518. 

' ' C h lor hy drm es, 516. 

" Ethers of, 517. 

Glyceryl, 484, 516. 

Bromide, — 518. 
Chloride, — 61. 

" Chlorhvdrine. 516. — 517. 

" Cyanide. — 518. 
Glycide, 517. 
Glycocoll, 244, 77. 



VI 



INDEX. 



Glycol, 92, 504. 

" Condensed, 506. 
" Sulphur, 505. 
Glycollic At id, 92, 505, 508, 509. 
Glvcolyl, 484. 
Glyoxal,511. — 512. 
Glyoxalic Acid, 511. — 512. 
Gold, 222. 

" Bromide, 225. 

" Chloride 224. — 226. 

(i Iodides, 225. 

" Oxides, 225. 

" and Sodium Hyposulphite, 225. 

" Sulphides, 225. 
Gothite, 378. 
Granites, 411. 
Graphite, 459. 
Graphitic Acid, 459. 
Gray Iron . 381. 
Greenockite, 359. 
Green Stone, 411. 

" Vitriol, 379, 384. 
Grove's Cell, 163. 
Guano, 343. 
Gum, 521. 

Gun Cotton, 66, 522. 
Gunpowder, 216. 
Gypsum, 308, 342. 



Hallovsite, 410. 
Halotrichite, 409. 
Hard Water, 340. 
Harmotome, 410, 456. 
Hauerite, 373. 
Hausmannite, 373. 
Heat, 13. 

" of Chemical Combination, 123. 

" ot Combustion, 117. 

" Expansion by, 14. 

" Latent, 16. 

" Sources of, 16. 

" Specific, 16. 

" Unit of, 14. 
Heavy Spar, 344. 
Hematite, 378. 
Hemihedral Forms, 145. 
Hemitropes, 150. 
Hercvnite 408. 
Hessite, 321. 
Heulandite, 410, 457. 
Hexagonal System, 140. 
Hexatomic Organic Compounds, 520. 
Hexylene lodo-hydride, 521. 
Hippuric Acid, 244, 77. 
Holohedral Forms, 146. 
Homologous Series, 475. 
Homologues, 475. 
Honey, 522. 
Hornblende, 356. 
Horn Silver. 220. 

" Stone, 445. 
Hydrates 80, 230, 445. 
Hydric Oxide, 201. 
" Peroxide, 202. 
" Persulphide, 312. 
" Selenide, 320. 

■ " Sulphide, 309. — 310, 311, 387. 
" Tellurite, 320- 
Hydriodic Acid, 210. — 84, 516, 520. 
Hydrobromic Acid, 210. — 84. 



Hydrocarbon Radicals, 483. 

Hydrocarbons. 474. 

Hydrochloric Acid, 208. — 84, 207, 209, 

239, 348, 493. 
Hydrocyanic Acid, 468. - 40, 371, 469, 489. 
Hydrofiuoboric Acid, 232. 
Hydrofluoric Acid, 207- 
Hydrogen, 201. — 202. 260, 478, 499. 

Alcoholic Atoms, 94, 244, 465. 

Basic Atoms, 94, 244, 465. 
Hydrogenium, 425. 
Hydromagnesite, 355. 
Hydro-silicic Fluoride, 452. 
Hydro-titanic Fluoride, 431. 
Hydroxyl and its Analogues, 202, 302. 
Hypochlorous Acid, 209. — 504. 
Hypochlorous Anhydride, 209. 
Hypophosphorous Acid, 252, 255. 
Hyposulphites, 315. 
Ilyposulphurous Acid, 313, 315. 



I. 



Ignition, Point of, 122. 

Ilvaite, 379, 457. 

Imides, 245. 

Indelible Ink, 221. 

Indigo Copper, 330. 

Indium, 359. 

Ink, 523. 

Iodic Acid, — 314. 

Iodine, 210 —493. 

Iodoform, 494. 

Iolite, 456. 

Iridium, 422. 

Iridium Compounds, 422. 

Iridosmine, 418. 

Iron, 377. —39. 

" Cast, 380. 

" Metallurgv of, 379. 

" Olivine, 379. 

" Passive Condition of, 384. 

" Pyrites, 308, 378. 

" Wrought, 380. 
Iso-acids, 491, 507. 
Isoamylic Alcohol, 497. 
Isohexylic Alcohol, 497. 
Isohexylic Iodide, 521. 
Isologue, 475. 
Isomaleic Acid, 514. 
Isomerism, 133. 

" in Lactic Family, 511. 

Isometric System, 138. 
Isomorphism, 68. 

Isomorphous Mixtures, Notation for, 274. 
Isopropylic Alcohol, 496. 
Itaconic Acid, 514. 
Ivory, Black, 458. 



Jamesonite. 27 
Jarosite, 379. 
Jasper, 445. 



Kakodyl, 261. 
Kaolinite, 410. 
Ketones, 495. 
Kieserite, 356. 
Kobellite, 279. 
Kupfernickel, 355. 



INDEX. 



vu 



L. 

Labradorite, 409. 

Lactamide, 244, 245. 

Lactic Acid, 94, 509, 511. — 524. 

Lactic Family, 507- 

" " Isomerism in, 511. 

" " Normal Acids, 508. 

" M Secondary Acids, 50 

" " Tertiary Acids, 511. 
Lactimide, 245. 
Lactmethane, 244. 
Lactyl, 484. 
Lakes, 412. 
Lamp Black, 458. 
Lanthanite, 334. 
Lanthanum, 334. 
Lapis Lazuli, 410. 
Laughing Gas, 239. 
Laurie Acid, 488. 
Lava, 411. 
Law of Ampere, 17. 

*' Definite Proportions, 9. 

" Gay Lassac, 48. 

" Mariotte, 12. 

" Multiple Proportions, 10. 

" Ohm, 159. 
Lazulite, 409. 
Lead, 316. 

" Soap, 515. 
Leucic Acid, 509. 
Leucite, 409, 456. 
Leukon, 454. 
Levulose, 522. 
Light, 174. 

Light Red Silver Ore, 220. 
Lime, 311. — 81, 432. 

" Chloride of, 341. 
Limestone, 340. 
Lime Water, 341. 
Limnite, 378. 
Limonite, 378. 
Linnseite, 338. 
Liquation, 272. 
Liquid State, 12. 
Litharge, 347. 
Lithium, 217. 
Loadstone, 383. 
Lunar Caustic, 220. 

M. 

Magnesia Alba, 355. 
Magnetic Carbonate, 355 

" Chloride, 356. — 331. 

" Hydrate, 354. — 81. 

" Oxide, 354. 

" Silicates, 353. 

" Sulphate, 355. 
Magnesioferrite, 378. 
Magnesite, 355- 
Magnesium, 354. — 61. 
Magnetic Pyrites, 378. 
Magnetite, 378. 
Malachite, 339. 
Malacone, 441. 
Maleic Acid, 514. 
Malic Acid, 515, 520. 
Malonic Acid, 505, 512. 
Malonyl, 484. 
Manganblende, 373. 
Manganese, 373. 



Manganese, Brown, 374 

" Red, Oxide of, 374. 
« Spar, 373. 

Manganic Chloride, 375. 

" Dioxide, 375. — 207, 300. 

" Hydrate, 375. 
Manganite, 373. 
Manganocalcite, 373. 
Manganous Compounds, 374. 

" Silico-fluoride, 452. 

Manna, 520. 
Mannite, 520. 
Mannitic Acid, 520. 
Marble, 340. 
Marcasite, 378. 
Margaric Acid, 488. 
Mariotte's Law, 12. 
Marsh Gas, 478. — 486. 

" " Series, 477, 478. 
Massicot, 346. 
Melaconite, 329. 
Melene. 477. 
Melissic Acid, 488. 

" Alcohol, 486. 
Menaccanite, 378. 
Meneghinite, 273. 
Mercaptan, 487- 
Mercuramine, 333. 
Mercuric Chloride, 335- 

" Cyanides, 467. 

" Iodide, 335 

" Nitrate, 333. — 334. 

** Oxide, 333. 

" Sulphate, 334. 

11 Sulphide. 334. —332. 
Mercurous Chloride, 334. 

" Chromate. — 399. 
" Nitrate, 333. 
" Oxide, 333. 
" Sulphate, 333. 
" Sulphide, 334. 
Mercury, 332. 

" Ammoniated Compounds, 335. 
Mesaconic Acid, 514. 
Mesitite,378. 

Metaphosphoric Acid, 253. 
Metastannic Hydrate, 436 
Metathesis, Conditions of, 37. 
Metathetical Reaction, 36. 
Methyl, 72, 484. 
Methylamine, 242. 
Methyl-glycollic Acid, 510. 
Methyl-phenyl, 483. 
Methylic, Alcohol, 485. 

" Hydride, 477. 
Miargyrite, 273. 
Mica, 356, 410. 
Microcosmic Salt, 254. 
Millerite, 335. 
Mimetine, 318. — 291. 
Minium, 347. 
Mispickel, 257, 378. 

Mixtures, Distinction from Compounds, 10. 
Molasses, 522. 
Molecular Condition of Gases, 17. 

" Compounds, 132. 

« Structure, 63, 76, 474, 476, 510, 
525. 
Molecular Weight, 18. 

" " Determination of, 126. 

Molecules, Definition of, 11. 

" Constitution of, 131. 



V1U 



INDEX. 



Molecules, Sum of Atomicities, 132. 

Molybdate of Ammonia, 321. 

Molybdenite, 321. 

Molybdenum, 321. 

Molybdic Anhydride, 321. 

Monatomic Organic Compounds, 485. 

Monazite, 441 

Mono-acetine, 517. 

Monoclinic System, 141. 

Monometric System, 138. 

Mordants, 412, 442. 

Morphine, k.49. 

Mortar, 341. 

Mosaic Gold, 438. 

Mucic Acid, 522. 

Multiple Proportions, Law of, 10. 

Mundic, 388. 

Muriatic Acid, 208. 

Myristic Acid, 488. 

Mysorin, 330. 

N. 

Nagyagite, 321. 

Names of Binary Compounds, 101. 
" of Elements, 101. 
" of Ternary Compounds, 104. 
Napthaline, 483. 
Natrolite, 410, 456. 
Natural Colors. 176. 
Naumannite, 320. 
Needle Ore, 279 
Niccoliferous Smaltine, 335. 
Niccolous Chloride. 366 
" Cyanide. — 371. 
" Nitrate, 386. 
" Sulphate, 366. 
Nickel, 365. 

" and Oxygen, 366. 
" Glance. 335. 
" Green, 365. 
" Vitriol, 365. 
Nicotine, 249. 
Niobium, 296. 
Nitres, 215, 216. 

Nitric Acid, 234. — 236, 238, 239, 240, 316, 
317, 347. 
" Anhydride, 236. 
" Oxide, 238 —236. 
" Peroxide, 237. 
Nitriles, 245. 
Nitro-benzol, 68, 482. 
Nitrogen, 233. — 467. 
Nitrogen, Bromide of, 250. 
" Chloride of, 250. 
" Iodide of, 250. 
" Oxides of, 234. 
Nitro-glycerine, 516. 
Nitrous Acid, 236. 

Anhydride, 236. 
" Oxide, 239, 240. 
Nomenclature, 100. 

" Lavoiserian, 102. 

Notation, 33. 

O. 

Octahedrite, 430. 

(Enanthylic Acid, 488. 

(Erstedite, 441. 

Ohm's Law, 159. 

Oil of Bitter Almonds, 501. — 77. 

" Garlic, 498. 

" Meadow Sweet, 504. 



Oil of Mustard, 498. 

" Vitriol, 318. 

" Winter Green, 504. 
Oils, Drying, 518. 

" Essential. 481,501 
Olefiant Gas, 479. — 486. 

" " Series, 477, 479. 
Olefines, 479. 

" Acid, 508. 
Oleic Acid, 498. 
Oleines, 518. 
Oligoclase, 409, 456. 
Olivine, 356. 
Onofrite, 320. 
Onyx, 445. 
Oolite, 340. 
Opal, Common, 444. 

" Varieties, 445- 
Optical Crystallography, 153. 
Orangeite, 441 
Organic Chemistry, 473. 
" Compounds, 4i3. 
Oriental Amethyst, Ruby, and Topaz. 
Orpiment, 263. 
Orthite, 441. 

Orthoacids, 229, 232, 235, 252. 
Orthoclase, 409. 
Orthophosphoric Acid, 252. 
Orthorhombic System. 141. 
Osmic Compounds, 420. 
Osmium, 420. 

Oxalic Acid, 464, 505. — 463. 
Oxamethane, 77, 244. 
Oxamic Acid, 77, 244. 
Oxamide, 76, 243. 
Oxatyl, 465. 
Oxalic Ether. — 499. 
Oxidation, 301. 
Oxides, Metallic, 82. 
Oxy butyric Acid, 509. 
Oxygen, 300. — 115, 125, 325. 
Oxygenated Radicals, 484. 

" Water, 202. 

Oxygen Compounds, 301. 

" Ratio. 451. 
Oxygen Salts, 88. 
Ozone, 302. 
Ozonides, 303. 



P. 



Pachnolite, 408. 
Palladious Nitrate, 424. 

" Sulphate, 424. 
Palladium, 423. 
Palmitic Acid, 488. 
Palmitines, 518. 
Paracyanogen , 467. 
Paraffine, 477. 
Paralactic Acid, 505. 508. 
Paraleucic Acid. 508. 
Paraluminite, 409. 
Parentheses, use of, 34. 
Parisite, 364. 
Pearl White, 276. 
Pelargonic Acid, 488. 
Perchloric Acid, 209. 
Perchromic Acid, 405. 
Periclase, 354. 
Perissad Elements, 201. 
Perissads, 59. 
Permanganic Acid, 377. 



INDEX. 



IX 



Perofskite, 430. 
Petalit*, 457. 
Petroleum, 458. 
Pewter 434. 
Pharmacosederite, 379. 
Phenols, 501. 
Phenyl, 482. 

" Alcohol, 502. 

" Series, 477, 482, 501. 

" Series. Acids of, 503. 
Phenylene, 4S3. 
Phoenicochroite. 406. 
Phosgene Gis, 483. — 508. 
Phosp bines, 253. 
Phosphoric Anhydride, 253. — 86, 489. 

Chloride, 256 —63,77,316,509. 
" Oxychloride, 257. 

" Sulphochloride, 257. 

Phosphorite, 3i3. 
Phosphorous Acid, 252, 257, 251. 
" Anhydride,- 252. 

« Chloride, 258. — 56, 493. 

" Iodide, — 497. 

Phosphorus, 250 — 255, 493. 

" Rel, 251. 

Phosphuretted Hydrogen, 255. 
Photography, 221. 
Physical Properties of Matter, 10. 
Physics, Definition of, 3. 
Pickeringite, 409. 
Picric AciJ, 502. 
Pimelic Acii. 512. 
Pink Salt, 435. 
Pisanite, 379. 
Pitchblende, 293. 
Plaster of Paris, 342. 
Platinic Compounds, 426. 
Platinous Compounds, 427. 
Platinum, 425. 

" Bases. 428. 
" Sponge, 418. 
Plumbates, 348. 
Plumbic Acetate, 347. — 348, 349. 

" Carbonate, 348. 

" Chloride, 348. — 349. 

" Chromate, 403. 

" Hydrates 347. 

" Nitrate, 347. — 40, 237, 240, 466. 

" Oxide, 348. 

" Peroxide, 347. —305. 

" Phosphate, 348. 

" Sulphate, 348. 

" Sulphide, 346. 

" Sulphocarbonate, 466. 
Poles, Positive and Negative, 165. 
Polybasite, 273. 
Polymerism, 134. 
Polymorphism, 133. 
Porcelain, 411. 
Porphyry, 411. 
Potassic Aluminate, 216. 

" Acetate. — 478, 489, 493, 494. 

" Bicarbonate. 216. 

" Carbonate, 215. — 467. 

" Chlorate, 209. — 300. 

" Chloride, 216. 

" Chromate, 403. — 300. 

" Cobalticyanide, 370. 

" Cyanate, 472. 

" Cyanide, 468. — 371, 469 3 472, 513. 

" Dichromate, 403. — 399, 400. 
Dioxide, 216. 



Potassic Ethvlate, — 472. 

" Ferricyanide, 470. — 469. ' 

" Ferrocyanide, 469. — 463, 469. 

" Fluoride, — 232. 

" Kluotantalate, 298. 

" H/drate. 216. — 82, 84, 209, 357, 
376, 483, 472, 480, 499, 504, 510, 
513. 

" Manganate, 376. 

" Nitrate, 216. — 238. 

" Nitrite. 233. 

" Oxalates, 464. 

" Oxides, 216. 

" Permanganate, 376. — 377. 

" Persulphide, 312. 

" Pyroaatimoniate, 269. 

" Rutheniate. 419. 

" Stannate, 436. 

" Sulphate, — 312. 

Sulphide, — 312, 466. 

" Sulphohydrate, — 312, 487. 

" Sulphocarbonate, 89. —466. 

«• Tartrates, 217, 268. 

" Tetroxide, 216. 

" Trichromate, 403. 
Potassio-ferrous Sulphate, 319. 
Potassio-iridic Chloride, 422. 
Potassio-iridous Chloride, 422. 
Potassio-magnesic Sulphate, 356. 
Potassio-osmic Chloride, 421. 
Potassio-palladic Chloride, 424. 
Potassio-rhodic Chloride, 422. 

" «• Sulphate, 422. 

Potassio-rutheriie Chloride, 420. 
Potassio-stannous Chloride, 435. 
Potassio-zirconic Fluoride, 440. 
Potassium. 215- —465. 

" Alum. 409, 413. 

Precipitate, Definition of, 33. 

" How represented, 35. 

" When formed, 37. 

Printing Ink, 460. 
Propione, 495 
Propionic Acid, 488. — 510. 

Anhydride, 493. 
Propionyl, 484. 
Propyl, 484. 
Propylene, 477. 
Propylic Alcohol. 485. 

" Glycerine, 518. 

" Glycol, 505. 

" Hydride, 477. 
Proustite, 220, 263. 
Prussian Blue. 470. 
Prussiates of Potash, 469, 471. 
Prussic Acid, 488. 
Psilomelane, 373. 
Puddling, 332. 
Purple of Cassius, 225, 437. 
Pyrargyrite. 220, 273 
Pyroantimonic Acid, 269. 
Pyrochlore, 293, 441. 
Pyrolusite, 373. 
Pyromorphite, 348, 291. 
Pyrope, 449. 

Pyrophosphoric Acid, 252, 254. 
Pyrophyllite, 410. 
Pyrotartaric Acid, 512. 
Pyroterbic Acid, 498. 
Pyroxene, 457. 
Pyruvic Acid, 511. — 512. 
'' Series, 511. 



INDEX. 



Quantivalence, 55. 

' ' of Radicals, 59*. 

Quartation, 223. 
Quartz, 444. 

" Varieties, 445. 
Quick Lime, 341. 
Quinine, 249. 

R. 

Radical, Atomicity of, 60, 132* 
Definition of, 83. 
Substances, 38, 131. 
Radicals, Acid, 83. 

" Alcoholic, 73. 

Basic, 83. 
" Compound, 38, 484. 
Raimondite,*379. 
Rammelsbergite, 365. 
Reaction. Definition of, 34. 
Realgar, 263 
Red Hematite, 378. 

' ' Liquor, 414. 

" Ochre. 378. 

" Oxide of Zinc, 357. 
Reduction 301. 
Remingtomiie, 368. 
Rhodic Salts, 421, 422* 
Rhodium, 421 
Rhodonite, 373. 
Rhombohedron , 140, 
Rinman's Green, 370. 
Roccellic Acid, 512. 
Rochelle Salts, 214. 
Roman Alum, 413* 
Rouge, 388 
Rubidium, 217. 
Ruby, 408. 
Ruthenium, 419. 
Rutile, 430. 

S. 

Saccharic Acid, 520. 

Saccharine Bodies, 521. 

Sal Ammoniac, 247. 

Saleratus,214. 

Salicine, 523. 

Salicylic Acid, 504. — 502. 

Salisrenine, 523. 

Sal Prunelle. 216. 

Sal Soda, 213. 

Salts, 86. 

" Acid, 87, 105. 

" Basic, 87, 105. 

" Neutral, 87. 

" Oxvgen, 88. 

" Sulphtir, 89*. 
Salt of Sorrel, 464. 
Sand. 445. 
Sandstone, 445. 
Saponification, 493, 515. 
Sapphire, 408. 
Sareolite, 456, 457. 
Sartorite, 263. 
Scalenohedron, 140. 
Scapolite, 410. 
Scheele's Green, 259. 
Scheelite, 322. 
Scheeltine, 322. 
Schorlomite, 379. 



Scolecite, 410. 
Scorodite, 379. 
Sebacic Acid, 512. 
Selenic Acid, 320. 
Selenite, 342. 
Selenium, 319. 
Senarmontite. 268. 
Serpentine. 356. 
Siderite, 378. 
Siegenite, 388. 
Silica, 444. 
Silicates, 446. 

" Native, 448. 
' ' of Organic Radicals, 454. 
Siliceous Sinter, 445. 
Silicic Acid, 445. — 86. 
" Anhydride, 444. 
" Bromide, 453. 
" Chloride, 452. — 61, 455. 
" Ethers, 454. 
" Ethide, 454. 
" Fluoride, 451. 
" Hydrates , 445. 
M Hydride. 453. 
" Hydrochloride, 454. 
" Iodide, 453. 
" Methide, 454. 
" Sulphide, 451. 
Silico-fluoric Acid. 452. 
Silico-fluorides, 452. 
Silicon, 444. 
Silver, 220. 
Silver Glance, 220. 
Slags, 380, 397, 447. 
Slate, 411. 
Smalt, 370. 
Smaltine, 368. 
Smitbsonite, 357. 
Soap, 214, 216, 515. 
Soapstone, 856. 
Soda-lime, 282. 
Sodic Alum, 413. 
" Aluminate, 414. 
" Arsenite, — 263. 
" Bicarbonate, 214. 
" Carbonate, 213. — 214. 331. 
" Chloride, 213 — 208. 
" Disulphate, 319. — 87, 316. 
" Ethide, — 496. 
" Ethy late, 473, 492. 
" Hydrate, 214. — 82, 84, 360, 412. 
" Hyposulphite, 315. 
" Methide, — 489. 
" Nitrate, 215. — 234. 
" Oxide, 215. 
" Peroxide, 215. 

" Phosphate, Common, 254. — 361 
'* Stannate, 438. 
" Sulphates, 319. — 35, 213. 
" Sulphide, 312. — 213. 
" Sulphite, 315- 
Sodio-iridic Chloride, 422. 
Sodio-platinic Chloride, 426. 
Sodio-rhodic Chloride, 422. 
Sodio-zirconic Fluoride, 440. 
Sodium, 213. — 481, 483, 492. 
Solder, 434. 
Solid State, 11. 

" " Symbol for, 35. 
Soluble Glass, 445. 
Solution, 107. 

" Curves of, 108. 



INDEX. 



Solution, Differs from Chem. Change, 110. 

" Ho.v indicated, 35. 
of Gases, 109. 
Spathic Iron, 378. 
Specific Gravity, 1. 

" " of Vapors, 21. 

" Heat, 16. 
Spectra by Absorption, 187. 

" Chromatic, 176. 
Spectroscope, 176. 
Spectrum Analysis, 181. 
Specular Iron, 378. 
Speiss, 335- 
Spermaceti, 488. 
Sphserosiderite, 378. , 
Sphene, 430. 
Spiegeleisen, 381. 
Spinel, 408. 
Spodumene, 457. 
Stannates, 433. 
Stannic Chloride, 435. 

" Hydrate, 433. 

" Oxide, 437. 

" Sulphides, 437. 
Stannous Chloride, 431. — 208. 

" Hydrate, 438. 
Oxile, 437. 

" Oxychloride, 434. 

11 Sulphide, 437- 
Starch, 521. 
Stearic Acid, 488. 
Stearine, 513. 
Steel, 382. 
Stephanite, 273. 
Stibines, 271. 
Stiboniums, 271. 
Stilbite, 410, 453. 
Stochiometry, 41. 

" Rules of, 42, 47, 48, 49. 

Strontianite,3±4 
Strontic Sulphate, — 345. 

" Sulphide, - 345. 
Strontium, 344. 

" Compounds of, 344, 345. 
Suberic Acid, 512. 
Substitution, 65. 
Succinamic Acid, 244. 
Succinamide, 243. — 245. 
Succinic Acid, 92, 505, 512, 514. 

" Series, 512. 
Succinyl, 434. 
Sucroses, 521. — 522. 
Sugars, 93. 

" Cane, 521. 
" Fruit, 521. 
" Grape, 521. — 35. 
" of Lead, 347. 
" of Milk, 521. 
Sulphantimonites, 273. 
Sulphates, 319. 
Sulphides, 309. 313. 
Sulphites, 314. 
Sulphoarseniates, 263. 
Sulphoarsenites, 263. 
Sulpho-bismuthites, 279. 
Sulpho-carbonic Acid, 466. 
Sulphocyanates, 473. 
Sulphohydric Acid, 309. 
Sulphur, 308. — 312, 314, 315, 316. 

" Anhydrides, 263. 

" Compounds with Oxygen, 313. 

" flowers of, 309. 



Sulphur, Liver of, 312. 
Milk of, 309. 
Scdcs, 89, 263. 
Sulphuretted Hydrogen, 309. 
Sulphuric Acid, 316. — 35, 33. 300, 314, 463, 
486, 491, 493. 
" " Norduausen, 319. — 316. 

Anhydride 315. — 35, 40, 86. 
Chloride, 319. 
Sulphurous Acid, 314, 316. 

Anhydride, 313. — 316. 
" Chloride, 319. 

Sulphurylic Chloride, 316. 
Sycocerylic Alcohol, 501. 
Syepoorite, 338. 
Sylvanite, 321. 
Symbols, 33. 

" Bracketed, 74. 
" Empirical, 69. 
" Graphic, 70. 
" Rational, 69. 
Synaptase, 523. 
Synthesis, 9. 
Synthetical Reaction, 35. 
Systems of Crystals, 138. 

T. 

Tabular Spar, 343. 
Talc, 358. 
Tannic Acid, 523. 
Tannine, 523. 
Tanning, 523. 
Tantalic Acid, 298. 

" Anhydride, 298. 
" Chloride, 298. 
" Fluoride, 298. 
Tantalite, 297. 
Tantalum, 297. 

" Compounds of, 298. 
Tartar Emetic, 268. 
Tartaric Acid, 519, 268. — 217. 
Tartronic Acid, 516. 
Telluric Acid, 320. 
Tellurium, 319. 
Tellurous Anhydride, 320. 
Temperature, 13. 
Tennantite, 263. 
Tension of Gases, 12. 
Tephroite, 373. 

Ternary Compounds, Names of, 104. 
Test Papers, 89. 
Tetradymite, 275. 
Tetragonal System, 139. 
Tetrahedrite, 273, 274, 330. 
Tetratomic Organic Compounds, 519. 
Thallium, 222. 
Thenard's Blue, 370. 
Theory of Exchanges, 189. 
Thiacetic Acid, — 77- 
Thomsenolite, 408. 
Thomsonite, 410. 
Thoric Chloride, 441. 
Thorite, 441. 
Thorium, 441. 
Tin, 433. 

" and Alcohol Radicals, 438. 

" Butter of, 434. 

" Pyrites, 433. 

" Salts, 434. — 439. 

" Stone, 433. 
Tincal, 230. 



I 



Xll 



INDEX. 



Titanic Iron, 378. 
Titanium, 430. 

" Compounds of, 430, 431, 432. 
Titanous Cnloride, 430. 

" Oxide, 432. 
Toluol, 477. — 501. 
Toluylic Acid, 503. 
Topaz, 409. 
Tourmaline, 228. 
Trachyte, 411. 
Travertine, 340. 
Triacetine, 517. 

Triatomic Organic Compounds, 515. 
Tribasic Acids, 85, 465, 518. 
Tricarballyiic Acid, 518. 
Triciinic System, 142. 
Triethyline, 517. 
Trimetric System, 141. 
Triphylite, 379. 
Triplite, 3/3. 
Tripoli, 445. 
Troilite, 3(8. 
Tufa, 340. 
Tungsten, 322. 

" Compounds of, 322. 
Tungstic Acid, 322. 

" Anhydride, 322. 
Turnbull's Blue, 471. 
Turpeth Mineral, 334. 
Turpentine, Oil of, 477, 481. 
Turquois, 409. 
Twin Crystals, 150. 
Type Metal, 265, 346. 
Types Chemical, 62, 69. 
" Condensed, 64. 
" Mixed, 65. 



Ultramarine, 410. 

Unit of Atomic Weight, 27. 

" Current, 169. 

" Electromotive Force, 169. 

" Heat, 14. 

" Molecular Weight, 27. 

" Quantivalence, 201. 

", Resistance, 169. 

" Specific Gravity, 2. 

' Volume, 2. 

" Weight, 2. 
Unitary Theory, 95, 132. 
Uranite, 293. 
Uranium, 293. 
Uranium and Oxygen, 295. 
Uranous Chloride, 294. 
Uranyl, 293- 

Chloride, 293. 

" Fluoride, 293. 

" Hydrate, 293. 

" Nitrate, 293. 

Potassic Sulphate, 293. 
Urea, 243, 472, 473. 

V. 

Valentinite, 268. 
Valeramide, 245. 
"Valerianic Anhydride, 493. 
Valeric Acid, 488. 
Valerolactic Acid, 509. 
Valeryl, 484. 



Valerylene, 477. 
Vanadates, 292. 
Vanadic Annydride, 292. 
Vanadinite, 291. 
Vanadium, 2wl. 

Nitride of, 292. 
" Oxides of, 291. 
Vanadyl, 291. 

Vegetable Kingdom, Function of, i 
Vermilion, 334. 
Vesuvianite, 458. 
Vinyl, 484. 

" Alcohol, 497. 

" Series, 497. 
Vitriols, 319, 3z9, 358, 379. 
Vivianite, 3/9. 
Voltaic Battery, 161. 
Voltaite, 379. 
Volume, 1. 
Vulcanized India Rubber, 309. 

W. 
Wad, 373 
Water, 201. — 80, 81, 202, 480. 

" of Crystallization, 94. 

" Glass, 445 
Waves of Light, 176. 
Wavellite, 409. 
Weight, 1. 
White Iron, 381. 

" Lead, 348. 

" Vitriol, 358. 
Witherite, 344. 
Wittichenite, 279. 
Wolfram, 322. 
Wollastonite, 457. 
Woody Fibre, 521. 
Wulfenite, 321. 



X, 



Xanthosiderite, 
Xylol, 477. 



Yeast, 523. 
Yellow Ochre, 378. 
Yenite, 379. 
Yttrium. 363. 



Zaratite, 365. 
Zeolites, 410. 
Zinc, 357. — 35, 387, 479. 

" and Alcohol Radicals, 358. 

" Butter of, 358. 

" Methide. — 478, 496. 
Zincic Carbonate, 358. — 361. 

" Chloride, 358. 

" Hydrate, 357. 

" Oxide, 357. — 361. 

" Sulphate. 358. — 54. 

" Sulphide, 361. 
Zinkenite, 273. 
Zircon, 440. 
Zirconia, 440. 
Zirconium, 439. 

Compounds of, 439, 440. 
Zoisite, 457. 



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